Type panel.ommasign.com into the address bar of your browser and hit Enter. Fill your credentials in the login form. Click Login button when you are done.
I) Authorize via SMS
Enter 6 digit authorization code sent via sms from your phone and click Send Code.
If you login from the same device, you will not be asked for SMS code in every login attempt for a certain period of time.
II) Authorize via Authy App
Download Authy app from here.
Register your phone number.
You will see the Ommasign on app list. Click to Ommasign.
You will see a 6-digit token. Type it in the login screen. Click "Send Code".