hi Medhat, to do so : *

1 - From the login (Sign In) page you can choose  Manage databases  

2 - That should reveals a page when you can see all your databases 

3 - After that you can select the desired database and click Backup button

4 - enter the master password and click Backup 

To restore a database click on the 'restore database' and a pop-up window should appear , enter the master password and choose your backup in the file field and click restore. 

Good luck