Usually, your institutional username and password will be enough to login to CLARIN password-protected services. In that case there is no need to register a CLARIN account.
In the following cases you will however need to register a CLARIN account:
Your university or academic institute is not listed in the CLARIN discovery service.
You are not affiliated with an academic organisation. In this case, please make sure to provide a clear motivation for your account request (e.g. describing your personal research interest).