1- Check data files path and free space by check DB properties.
2- Drop current database to be replaced by either:
a- Right click on DB and Delete: In case users connected it will give a warning. In case of any job running please stop it and do delete again.
b- Right click and de-attach(It will stop database and you require to delete the data files manually. In case of users connected they will be disconnected. You can also move the files and re-attach to another database kind of cloning). Be sure to uncheck the Drop option since it will take longer time then delete the files manually.
3- Start TSM client and expand tree till you reach the target server. Right panel search for the target database you want to restore from and select the Full-Backup and right click select restore to alternate
From below screen be sure to select the new instance name and exact path and start the restoration. The most important is to select “Restore to a new database” and select the target database.