Until you get the lecture, here are some "rules of thumb":
You wear your uniform on duty, as well as on your way to and from work (normally - some exceptions may apply, i.e. if the "threat" level is high).
Thus, you can stop and pick up a few things on your way to or from work (within reason: eggs, bread, milk ... but you should wait until you‘re back in civvies before you go for a final fitting at the local "Lusty Leather Lovers" S&M shop ...)
You‘ll learn all about this eventually, including how to request permission from your CO if you want to wear your uniform to a social function (e.g. mess kit as an equivalent to "black tie")
You do NOT wear your uniform any place where to do so would bring disgrace upon the Army (i.e. "aerobic exercise bars" - where your heart rate goes up as the clothes come off ... don‘t anybody tell Tree Hugger, or she‘ll probably go off the handle again, but some hetrosexuals actually enjoy watching attractive members of the opposite sex disrobe ... and the ones who can‘t accomplish this with their wit, natural charm, intellect and rugged good looks sometimes resort to "aerobic exercise bars" ...)