Can you select multiple computers and apply the same action on all selected computers?

Yes, to select multiple computers, click on the Computers column header in the grid to call out the Actions Toolbar. Then in the Actions Toolbar, you can select all the Computers or specific Computers from the drop-down list and click on Select Computers button once you have made your selection. 

Alternatively, you can click on a particular Computer name to call out the Actions Toolbar for that Computer, then click on the + icon beside the Computer name and select the additional Computers from the drop-down list. Once the selection has been made, click on the Select Computers button to finalize your selection.

Once selected the Action Toolbar will indicate the number of systems that are selected allowing you to take action on all of them at once.