You buy tix through NAAA. The mids sit on the Blue Side, lower level, near the closed end of the stadium. Seats near the mids are nearly impossible to get -- they've typically been held by people for YEARs or go to VIPs.
In my day, mids (other than plebes, I believe) can get single game tix to sit with parents or others and these are located on the upper level directly above where the mids sit as a group. I believe this is still the case today. If I remember correctly, the mids are offered the opportunity to buy the tix -- obviously, you can reimburse them. Their "package" includes their own seat and the ones for their guest, so they can sit w/you. In my day, this wasn't an option for plebes.
If you want season tix, you'll prob get whatever the best available currently are. Chances are they will be Gold side ("visitor" side) across from the mids, probably upper level. If you want single game tix, I'm not sure where they will be located as I haven't bought those in years. It may depend on how many seats you want together -- the larger the number, probably the worse the seats.
If you buy season tix, you are offered the opportunity to buy tix for away games as part of the package. The seats are typically excellent -- better than at USNA. As for only single game away tix (i.e., not part of a season tix package) -- again, through NAAA.
I suggest you check out the NAAA website -- it has lots of good info on tix.