Not Learning Exactly What Job Description Says

So your profile says you are an anon 1st year analyst, so I am using that in my assumptions here (hence, if you have more experience, or more context to add, do so).

This sounds like example of where you need to a "team player" in all fairness/honesty. It sounds like you are at a busy/active firm, thus I don't get the impression are sitting around bored with nothing to do. So, you just may be more needed/valuable at you are doing (which you don't state). This is the real world, you do what the firm and your team/manager needs, not necessarily what you want to do (especially as a 1st year). Don't feel bad about this, this happen to TONS of people and really there is nothing wrong with it. They may also prefer to see you get more experience in time/grade before handing off acquisition tasks, or maybe the seniors at the firm really like doing it themselves and only call on analysts when they get too busy. Impossible for me to say, but development is as much of a team sport as any part of real estate, and this is what feels like at times.

That said, never hurts to share your desire to help out on the acquisitions. If you are wiling to working longer/later than you already are, volunteer your time (by saying "hey I have some extra capacity right now, do you need any help?" to the right people). Or even taking initiative and doing some research or other value-add on the sites being considered (i.e. don't wait to be asked). Still, most important that you do your main job/assigned tasks first and hyper-well, never lose sight of that.

Should you reach out to brokers? I mean, keeping those relationships active makes sense. How aggressively you should work on this is hard to say. If your role allows/expects you to source and prospect for deals, then of course. If it's not really expected, tread lightly. Nothing is more annoying than an eager analyst pushing shitty or less than stellar deals they "find" because they want sourcing credit for the sake of sourcing credit. If you push any deal forward, make sure it really fits the box, in truth the eagerness to do this at a junior level is not always as welcome as one may think (in fairness, this can vary greatly by firm and team culture). 

I'm assuming you are totally nailing your current job/role/assignment and are in the "have some free time" zone to be asking this question, if not.. get there first before coming back to this topic!