Once you have exited the modeling window, initiate the meshing process by clicking on Mesh in the Workflow.
Set Mesh Boundary Layer
AIM will prompt you to fix the boundary layer before generating the mesh. Click on Boundary Layer under Mesh Controls. Select the inside and outside faces of the fluid flow volume.
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 will detect that you are ready to generate the mesh and highlight the buttons in blue.