Yes, you can. At least I can with mine on unlimited computers.

Yes.  I have it installed at the office and at home. Your EFIN is only good for Efiling from one address though. I only Efile from the office.

how to install ProSeries on two different computers

how or what steps did you do to install on 2 different computers

Once you get this established, be VERY CAREFUL about which file you use to e-file. You will be copying data from computer A, carrying it to computer B, mess with it on Computer B, then later get a call while you are at Computer A and do input that is not on Computer B. When you are ready to e-file, which one should you use?

BE VERY CAREFUL. I recommend you always process the e-file from only one of the computers and remember BACKUP, BACKUP, BACKUP RINSE AND REPEAT.