I'm going to work from the assumptions that A) YOU haven't actually investing anything in this grant, and B) the grant was recently made.
At this point, you've got a promise ... nothing more. And that promise is, presumably, based upon your future actions (staying with the company).
SO, I'd create 4 investment reminder transactions (1 for the completion of each annual vesting periond). And when the reminder comes due, record a ShrsIn transaction reflecting the shares you've "earned".
You can probably record the reminders in any available investment account (i.e., your primary account), but you probably want to set up a separate Investment account for the ShrsIn transactions, so that -- when the occur -- the don't mess up the balance of any other account.