...
Change the view to Translucent display using the view dropdown selection in the upper region of the window. AIM will prompt you to fix the boundary layer before generating the mesh. Click on Boundary Layer under Mesh Controls. The boundary layer will be applied to the face of the cylinder inside of the flow volume.
Generate Mesh
Return to the Mesh panel, then click Generate Mesh under Output or at the top of the screen by the status window for Mesh. AIM should detect that you are ready to generate the mesh and highlight the buttons in blue.