"I'm mainly worried about the biology section, because all I did was guess on this test, and any other test because I haven't taken any bio classes yet, so I had no idea what to do. Any suggestions?"
I honestly would suggest taking the OAT at a later date. When are you taking bio classes? This is just my opinion but the OAT is an exam that you only want to take once . . . and you want a fantastic score the first time you take it. DON'T take the exam until you are READY!