At main menu click on Settings >> Estimate settings tab
Estimate settings
Default estimate template: The estimate template that is set for new estimates (you can change it per estimate) You can preview the look of the selected template.
Estimate prefix: Estimate numbers may optionally be prefixed with a group of letters (P.E estimate number may be: EST10001)
Starting estimate number: if there are no estimates recorded yet then this will be the first estimate number
Customize estimate text labels: if you would like to change the various texts that appear on the printed estimate, modify these values.
Predefined terms and conditions text: the default terms and conditions text that is set for new estimates (you can change it per estimate)
When you've finished editing the fields, click on "Save settings" toolbar button.