You can use TempVars, custom object or user table to store and retrieve user data. There is also a widely used function named fosUserName, which I prefer. If you use that, make sure you get a version that was written for 64 and 32 bit. If you're sharing a Windows login (i.e. if there is a generic login or I log in, do my thing and leave the pc for someone else to use in that state) then that function is of no use to you. The idea of it is to grab user Windows login and pc id if you want that too, and do away with login forms, passwords and all that maintenance. Then you match table Windows login against what code retrieves and you know who it is. If that login isn't found, they don't get in.
To simply answer your last question, the data about the currently logged in user is in the table, no? FName, LName, EmplID, etc?
EDIT - forgot to say welcome to the forum!
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.