You can setup your profile signature so that you can insert your signature into any document at the click of a button.
To setup your profile signature, click the round icon on the top right, then click 'Account Settings'
There are 2 ways you can setup your profile signature:
Option 1 - Draw your digital signature
Click 'Edit Signature' then draw your signature with your mouse and click 'Save Changes'.
Option 2 - Upload your digital signature file
Click 'Upload' then select your signature file. It will automatically be saved against your profile.
Note - if you need to create your own signature file, you can use this website here.
After your profile signature is setup, while you are creating a new document you can click 'Use Profile Signature' to insert your signature into any document!