In the navigation bar, when clicking on trips you will be able to create a trip via the green button:
In the next screen you can specify the locations 'From' and 'To' (and add more locations by clicking on the "+"), fill in the name of the trip and add a comment. The timeframe is optional. You can already activate the per diems as well by clicking on "Enable daily travel per diems".
Once created, you will be able to select this trip in the overview of your 'Trips'-menu and the trip field will appear in the expense form.
If it is determined in the 'Company Settings' that there is an approval necessary on your created trips, the trips will not appear in your drop down menu before they have been approved.