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 a Facebook account, you can use that to log into MuseScore.com.
If registering with your email address, you will be sent a verification link. Open that link to activate your account and log in for the first time.
You'll be taken to the MuseScore dashboard when you log in. If your account is new, on the left you'll see some other MuseScore users you can check out and follow if you wish. Later, this area will show activity from people you follow. On the right, there will be links to groups and to upgrade to a Pro account. Later, this area will show groups you are a member of, and, with a Pro account, statistics for how many times your scores have been viewed.