Do you have to vent the engine like a 2 cycle?

Two cycles do not have a vent, fourstrokes do.

What brand and model engine do you have?

I have an os70 surpass, and was wondering what how I run the vent line, directions says to you dont have to connect it to the muffler, so what do you do with it than?

If you are talking about the fuel tank vent, go ahead and connect it to the muffler. The crankcase vent is another story. Do NOT connect it to your muffler. If you have a tubing nipple on your intake manifold, run a piece of fuel tubing from the crankcase vent to the intake manifold. If there is no nipple on the intake manifold, just let the crankcase vent to the atmosphere.

Easiest way use a 3 line system ,fuel pickup line with clunk to the carb
one long enough to fuel with (then use a fuel plug to cap after filling)
the third to the nipple in the muffler then just a short piece on the crankcase
nipple out the bottom of the plane (vent). With the carb on the rear of a 4 stroke
trying to fuel through that is very unhandy. Really no different set up than a 2 stroke .

You are talking about the crankcase vent. It is on the bottom of the engine. That is where used oil drains out of. If you plane has a cowl, run some fuel tubing down through the cowling to the outside so the oil drips out, and doesnt mess up the cowl. If no cowl, you can add fuel tubing or not, but if you don't it will blow back into the rest of the engine or the firewall.