For a new staff member profile creation, a vendor must be logged in to their Vendor area. The vendor can initiate the creation of a new vendor staff account from the Vendor Staff Members page (My Account > Staff Members):
The vendor needs to click the "Add staff member" button and specify an email in the new blank field that opens in that section.
That must be a valid email address since the marketplace will use it to send an invitation to the user with a link for access to the vendor area. The prosperous vendor assistant will have to use that link to complete the sign-up to their profile as a staff member.
Before saving the new user profile, the vendor also needs to set the desired access level for the user by adjusting the Full access toggle for a profile. For more info on vendor staff access levels, see Multiple profiles for vendors: Staff member access levels.
If necessary, the vendor can add more than one staff member at once: every click of the "Add staff member" button creates an additional blank line for a new vendor staff member profile.
After adding the staff email address(es) they require and setting the access level(s), the vendor must click the Save changes button. That will create the new vendor staff profile(s).
Once a user profile for a new vendor staff member has been created, the vendor needs to send them an invitation so they can log in to the Vendor area, confirm their staff status and begin their work.