GoToSocial does not provide its own webclient, but implements the Mastodon client API. You can use this server through a variety of other clients:

Semaphore

Semaphore is a web client designed for speed and simplicity.

Use Semaphore

Tusky

Tusky is a lightweight mobile client for Android.

Get Tusky

More clients

Or try one of the clients listed on the official Mastodon page.

Get Mastodon apps