If you want to have a specific activity type set for a project/case, you can set it in "My name"->Settings in the Billing tab.
At the bottom of the Billing page, you can add a new activity, which will then be recorded on the case page, or you can search for existing activities and edit them.
These activities will then be displayed on the case page. Once you select a specific case from the grey menu on the left side of the screen, using the "gear" icon you will be taken to a page where you select the Billing tab.
At the bottom of the "Billing" page, you will find the "Activity Pricing Settings" list, where you can select the activity, its hourly rate, and the billing method (Type of Billing).
These configured activities for this case will then be displayed on the "Create Timesheet" page, which you can access using e.g. the "plus" icon.
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