How to sign?

Aside from the document you'll see a menu with actions, at the bottom you'll see two options - to sign manually or digitally.
If you want to sign manually - click Manually signature. You will see a small window where you can sign in using the mouse.
If you want to sign digitally - click digital signature. You will see a small window to the right, there are two buttons - Signature and Close. Click Signature, if you want to sign the document.