This is very easy, click in the "Edit Post View" icon and activate Deformation, then click in RESULTS:
Here you can choose between "%Model" and "Absolute". For instance, if you run a nonlinear analysis with "large displacement effect" activated then you may want to see displacements results at real scale, ie, 1:1. In this case choose absolute and enter 1.0 in the scale.
But please be aware that in general in linear static analysis (SOL101) deformed shape is exaggerated by nature, please note we run with the assumptions to have "small displacements & small deformations", then we want to see the "trend" of the results, if you plot results at scale 1:1 then you won't see any deformation, OK?.
Note that you can get to the Set Deformation dialog directly by right clicking on the PostView on the Post Processing Navigator and selecting "Set Deformation..."