After a user has accepted an invite to a Final Draft 13 site license and create an email and password, they can sign into Final Draft 13 by downloading and installing the program from here: www.finaldraft.com/download
After opening Final Draft 13 for the first time, they will be asked to sign in with the same email and password they created, which will allow them full use of Final Draft 13's features.
A site license user may only be signed into Final Draft 13 on one computer at a time. If that user wants to sign out, they can do so by going to Help in the menu bar and clicking Sign Out:
If a user forgets to sign out and tries to sign into Final Draft 13 on a second device, they will receive a prompt that they're signed in on too many devices. If they accept the prompt, Final Draft 13 will automatically sign out on the previous device and sign in on the new device.