To update MyMuse with the latest file, follow the same procedure as installing. It is alwasy good practice to MAKE A BACKUP before major changes.
It will not touch your database and will simply overwrite old files with new ones. In case of emergency, have a backup.
MyMuse also uses Live Update. Go to Components->MyMuse to see the welcome screen. Live Update will inform you if there are updates available.
You must enter your username and password from the MyMuse site in the options screen to be able to receive the updates