Open the Solver by double clicking under the Steady State Thermal project.
When the solver opens, click on in the Outline window to open the Mesh menu in the menu bar. In the Details window, expand Sizing, and change the Element Size from Default
to 0.5 m
(Make sure the units are set to meters by selecting Units > Metric (m, kg, N, s, V, A) in the menu bar)
When the sizing has been specified, press Mesh > Generate Mesh to create the mesh.