You need to be the owner of the workspace to be able to add members in it.
To add members to your workspace
make sure they previously created an account in Pimento. If not, ask them to follow this link: app.pimento.design/auth_flow=signup.
click on your workspace name in the top-left corner, and click on "Settings"
in the "Members" section, click on "Invite members"
you just need to write their emails. Once logged in, they'll be able to directly access your workspace