Select the Line tool . If
necessary, press and hold another shape tool in the toolbox, and
then choose this tool from the list that appears.
(Optional) In the options bar, select the Geometry options
triangle to use the following options:
Arrowheads Start and
End
Renders a line with arrowheads. Select Start, End, or
both to specify on which end of the line arrows are rendered. The
shape options appear in the pop‑up dialog box.
Choosing options for an arrowhead
Arrowheads Width and Length
Specify the proportions of the arrowhead as a percentage
of the line width (10% to 1000% for Width, and 10% to 5000% for Length).
Enter a value for the concavity of the arrowhead (from ‑50% to +50%).
Concavity
Defines the amount of curvature on the widest part of
the arrowhead, where the arrowhead meets the line.
In the Weight box, specify the width of the line in pixels.