The following procedure will help you to edit the VM storage policies of a VM:

Connect to the vCenter Server using the web client and switch to the Host and Clusters view using the key combination Ctrl + Alt + 2 (since this activity is performed on a VM, you can use the VMs and Templates view as well, using the key combination Ctrl + Alt + 3).
Right-click on the desired VM and navigate to VM Policies and Edit VM Storage Policies...:

In the Edit VM Storage Policies window, choose a VM storage policy to apply to all the associated files or assign individual VM storage policies to each of the items. Click OK to confirm the settings:

Once done, select the VM and navigate to its Monitor | Policies tab to view its policy compliance status: