Use the Accels tools on the Structure ribbon to apply g-Loads and angular velocity/acceleration.

Before running an analysis or optimization, you need to define at least one load case, which is a set of loads, displacements, accelerations, and/or temperatures that act on your model. You may also want to create multiple load cases with different loads and displacements to understand how this impacts the results of an analysis or optimization. As a general rule, accelerations should be applied to non-design spaces rather than design spaces.