You can lengthen or shorten a member by clicking and dragging one of its end points. Note that if your member has multiple segments, you can lengthen/shorten the individual segments.
To lengthen or shorten a member:
Select the member. A grab handle is displayed at each end of the member.
Hover your pointer over the end
you want to stretch. The Lengthen cursor is displayed.
Click and drag to stretch the member to the desired length, then release your mouse button.