Step 1: Open a new document and create a line with either the pen tool or the line too. Make sure you select the line by clicking it.
Step 2: Go to Window > Stroke, to open up the Stroke panel.
Step 3: In the stroke panel where it says “Arrowheads” You can select the arrow you want. The first one is the beginning the second one is the end. The beginning is the first point create and the end is the last point you created.
You can use scale to adjust the size of the arrow head.
Ta-da you create a line with an arrow!
This method is similar to Adobe Indesign, hope that helps!