Basically, your engine has what are called 'factory settings'. Sometimes these are supplied along with the other reading material in a box, sometimes they are not. It's important to find out what they are, so that you can ensure that for your first start, they are at proper manufacturer recommended settings. Having said that, in many cases, factory settings are too rich for a new engine to stay running (the combination of bogging and drowning in fuel and the tightness of the cylinder just makes normal running impossible). So, in most cases, what you'll need to do is slightly lean the high speed needle (and possibly the low speed needle (again these things will be identified in the manual for you, do not worry) and/or adjust the idle screw) in order to get the engine running. Do this with the wheels off the ground obviously.

Once the engine is running, the wheels are probably spinning, perhaps quite fast, this is normal, no need to try to stop them unless they start going really fast and destabliising the model, in which case, dab the brakes on the controller or adjust the idle screw outward. Once it runs, you can put it down and SLOWLY start running it round. Don't go over 1/3rd throttle, and after a couple of mins running, bring it in for a temperature check (if you don't have a temp gun, get one from a hobby store, they are not expensive and extremely useful), you are aiming to get the engine head up to about 200F, try to get as close as you can without going too much over. If this proves impossible during the first tank (for example, it's only getting up to 150), finish the tank anyway, then bring it in and lean out the high speed needle a TINY bit (never make adjustments bigger than an 8th of a turn when tuning, at least not while you're new at it) and try again, you need to get the engine up to temperature, only when you've done so does the real break-in start proper. Many people have killed engines early, despite doing 10 tank break-ins, the engine never got over 130F cos it was so rich, this is not hot enough to properly mate the surfaces in the engine.

Basically, with this method of running it around, not too fast, getting it up to temperature, shutting it off and letting it cool, then repeating, is the 'cycle' process that beds the piston, sleeve and liner in. They need to get hot and cold several times before the break in can be considered 'done'. Some people are positively anal about this process, not going over half throttle til they have 10 tanks or so of cycling through it. Others are very gung-ho, 3 tanks at most. I tended to do about 4-6 tanks depending on the value of the engine (more expensive, longer process), which was about 20 cycles I guess, before giving it the beans, but many would say that was also more than needed. Of course it is not possible to do 'too much' break in, but it is possible to do too little. For your first time, I'd do quite a few cycles to be sure. Just to clarify, you do not need to use a whole tank to get it up to temp each time, just run it til it gets to about 200F, then shut it off, let it cool to below 120 and start it up again. Depending on the engine you may be able to get four or even 5 cycles per tank. The important thing is to keep the high speed needle rich during break-in, don't be tempted to speed up this process by leaning it out to much to get it up to temperature faster, the excess oil during break-in is important. You only want to lean it enough to get the engine up to temperature gently.

Once you're happy with the break-in, you can start giving it full throttle and tuning for power. There are many videos about this, but basically, it equates to leaning the high speed needle 1/8th of a turn at a time, and testing in between, to get a nice smooth accelerating sound, good performance and a nice thin trail of smoke. Don't worry too much about engine temperature unless it is dramatically low or high (under 180 or over 300), the most important thing is the smoke. A little smoke (doesn't have to be a lot) means your engine is getting oil, no smoke means it is not getting enough. Great plumes of smoke means its getting more than it needs (and can also be detrimental). It's always better to have too much smoke than none at all, but we're aiming for nice thin grey consistent wisp when accelerating. A good operating temperature is anywhere from 220-280F.

Hope that helps, there's a lot more to it than that of course, it's an artform at the highest level, but that should give you a general idea and get you running without any major disasters for your first engine.