Welcome to MuseScore! Go to https://musescore.com/user/register and enter a username, email address, and password you’ll use to log in. Alternatively, if you have an Apple ID, Facebook, or Google account, you can use them to sign up.
If you sign up with your email address, an activation link will be sent to it. You need to open that link to activate your account and log in for the first time.
Once you're logged in, you'll be taken to the MuseScore dashboard. If your account is new, you'll be asked to choose the categories you like the most. Later, this page will show the activity of people you follow.