GoToSocial require a dedicated root domain, for example: gotosocial.domain.tld.

This package is not-working single-sign on or LDAP integration.  
You will have a separate account from the rest of your Yunohost server, potentially with a different username and password.

You can login to [gts.superseriousbusiness.org/admin](https://gts.superseriousbusiness.org/admin/) to administrate your GoToSocial instance.
The [source code of this administration panel](https://github.com/superseriousbusiness/gotosocial-admin) is available on github.