Do you mean install a second workstation as an admin workstation on an already existing ProSeries network.  I do not suggest doing that.

If you mean right clicking on an already existing ProSeries shortcut on your current workstation and selecting run as admin... that is perfectly fine.

This is the term admin used to describe two different actions.  This can be confusing, but the "Run as Admin" action in Windows elevates an executable's privileges in Windows, where as the Admin Workstation in ProSeries has a few more privileges in the ProSeries application in comparison to a normal user workstation.