If you have all the passwords, and know exactly which certificate to use to create said user, then all you should need is to launch the Admin client, create the new user and click on Register Now.
To create the new user in the Admin client, you probably need to select the proper domain first, then select the first tab (People & Groups), then use the right-hand menu to get the Registration dialog box.
Of course, utmost care must be taken in entering the details, otherwise a correction will have to be done at a later point.
Pascal.