You will need to do the following to setup a Partner User.
Seach for the Subcontractor Company in e-manageONE and make them a Partner User.
Create a new user in the e-manageONE Administrator. You will need Administrator rights to do the following.
Enter a Username and Password (You can use the Company name as the full name and the user)
Select the Subcontractor checkbox.
Select the Subcontract company from the dropdown list. The list only shows companies that are subcontractors.