Within Teamwork, you can upgrade an existing collaborator to standard user so they can be granted a wider range of permissions on your projects and site.
Go to the People tab at the top of your site and select the People subsection.
From the list of people on your site, click the name of the relevant collaborator to view their profile page.
In the top right corner of their profile, click the options button (three dots) and select Upgrade to Standard Account from the dropdown menu.
You will be asked to confirm if you want to upgrade the collaborator. Click OK to save the changes.
Alternatively, you can click the three dots to the right of the user in the list of people and select Edit Profile.
In the user details modal, you can change the Type field to Standard User. Click Update to apply the change.
For more information, see: Upgrading a Contact to a Collaborator