To generate surface meshes from the contours in your DICOM RT file, choose Generate Meshes from the main menu. Here you can choose which contours you would like to generate meshes for. And previously generated meshes are overwritten, but it is quick and easy to regenerate them if you need to.

Tick the boxes next to the contours you want meshes for, and click on generate. When this is finished (it only takes a few seconds), you can close this dialog, and see and interact with your meshes in the 3D viewport.

Resolution

The resolution options control how fine the final mesh for your contours will me. Large numbers indicate a coarse mesh, which is faster to generate. Smaller numbers produce a finer mesh which will be more conformal to your contours. Generally you want to choose a resolution that is around the slice thickness of the underlying CT data - 2 to 5 mm is usually a good number to start with.