Menu: View results->Contour lines
Toolbar: 
This display option is quite similar to Contour Fill (see Contour fill), but here the isolines of a certain nodal variable are drawn. In this case, each color ties several points with the same value of the variable chosen.
Here the configuration options are almost the same as the ones for Contour Fill, with the only difference being that the number given in the Number of Colors option will be used as the number of lines for this contour lines representation.
Contour lines are supported for results defined over nodes or gauss points.
If the gauss points results can be globally smoothed, then a Smoothed sub-menu will be added with a list of the gaussian results, see View results menu
Go to Preferences --> Postprocess --> Contour fill and lines to set and manage contour fill and lines options, like the number of colours, the colour map used, etc. Contour fill and lines
Go to Preferences --> Postprocess --> Legend and comments to manage the legend options, like size and style. Legends and comments