Simple. Just play games in live chess; the computer already searches for opponents it deems around your level! (you can change the deviation in your settings, but I recommend just leaving it the default).
The first several games you play though will probably not be players around your level. The computer is kind of guess and checking how you do against variously rated opponents to get a better idea of your rating. The formula ("k-factor" in elo/glicko rating systems I believe) updates after every game, so the more games you play - then the better job the computer will probably get at pairing you against equally rated competition. Eventually, the computer will almost always pair you against players within 100 or so rating from your level (but it may take several games before the computer "has a better idea" of your rating 
Hi, I am an absolute beginner and would like to start playing online chess. Is there any way I can set my experience level to play with someone of comparable, or somewhat better, experience. I don't mind losing most of the time, or all of the time, but I wouldn't want to bore an expert with my complete lack of expertise.