You can add a job arrive signature message, this is what the customer will read when the engineer arrives and if they agree they will sign.
In order to edit this message, first, open your system settings. From the 'Mobile settings' section, click 'Job arrive signature message'.
You will see a page with 2 choices. Click 'Yes' in order to set up this message. Then you will see a box where you can enter your message. When you are happy with this message click 'Save'.