On the right hand side of the screen near the users name, click on the downward arrow near the user logo to bring up User Settings.

Scroll down until you see Markups

You can amend the existing Name and Markup percentages or create your own by adding details in the field labelled "new markup".

Select your default markup by selecting an option from the drop down.

Click "Save Changes" once complete.

To change markups on a particular job, Edit the Job details and change Customer Type.