Open Workbench. Drag and drop a Modal system from the Toolbox onto the Project Schematic.
Right click the Geometry cell and Import the geometry file you are showing above.
Double click on the Model cell, Mechanical will open.
In Mechanical, click on Modal in the Outline, click on the Environment tab in the ribbon. Select the top edge and click the Fixed support.
Under the Geometry branch, find the plate and assign a thickness. Change the material if it is not Structural Steel
Click on Solve. The plate will mesh and the Modal will run.
When the solver has finished, right click on the Solution branch and insert a Deformation plot. Now you can see the shape and frequency of Mode 1.
Repeat for as many modes as you requested. The default is 6 modes.