When using the License Management portal, this allows you to create teams, activate domain(s) and assign seats to teams. This also allows you to invite co-admins or team admins that will have permissions to make changes within the License Management portal.
In terms of inviting end users (which do not need to be admins), this is simply done by these users creating their own Pantone Connect accounts using the activated domains at the login screen of Pantone Connect. If the users already have Pantone Connect accounts that use the activated domains, they can simply log into this account and it will recognize the domain and they will have full Premium access.
Please know that the License Management portal administrator(s) does not need to consume a Pantone Connect seat. The License Management portal is only for setting up and managing the license, whereas ‘users’ of the license/seats do not need access to the License Management portal but simply can create and log into Pantone Connect applications with the activated domain.