Well, I am going to take a guess here about your situation. I suspect you are one of those intellectually gifted people who have finished high school and been admitted to university well before the standard age. Your posts hint at this, as does your choice of a screenname (presumably derived from the famous physicist Richard Feynman). However, doing these things before standard age, you have missed out on social opportunities of interacting with your peers - something made worse by the fact that you probably had to spend a higher proportion of your time on your studies simply because you compressed them into fewer years.
If the above is the case, I think you are wise to want to increase your social interaction with your peers. There is a critical period to learn certain social skills, which you haven't missed yet - after a certain age learning those social skills becomes more difficult (though not impossible), because obviously social expectations are different for people as their age rise.
In any case, to answer your question, even if you are a senior at university, there is no reason you cannot interact with freshmen. You will probably not get to take many classes with them, that much is true, but you can always join a club that will provide you with regularized interaction opportunities. I am assuming you have the spare time to join a club, but if you do not, you are probably going to have a very difficult time finding and dating women in other ways anyway, since relationships do take time. Pick something you enjoy doing that also provides interaction opportunities. Unlike an advanced class on non-Euclidean geometry, a club is likely to have people from all years and subject fields. Good luck!
