if its the RTF version then the engine has been pre-broken in for you just run it in the method outlined in the manual.OS engines require little break in even out of the box a simple run in with some needle adjustments out lined in there manual.

the OS46 fxi runs well out of the box at least mine did before you fly it you should have it thoroughly looked over by a expeirenced pilot and make sure it will pass radio check, my engine ran well on my NEXTAR RTF but would not pass radio check and I had to run the antenna outside of the fuselage to work properly.

a few tanks run in the engine with it tuned rich, before you lean it out for optimal performance.
the ready to fly plane has a needle limiter so you shouldn't be able to lean it out much
as it is.

if its a arf and you have a new engine that has never been run before then do it by the book it came with depending on which engine brand you chose each has there own break in routine some more involved than others.