The quickest way is to drag and drop in the pin planner. You can grab multiple nodes or and busses.
The ports allow a special nomenclature whereby the bus is grabbed even if the index isn't listed. I try to use wildcards though for assignments that allow them. The Assignment Editor pull-down menu should have an (allows wildcards) by assignments that allow them, but I have seen assignments except them even thought it didn't explicitly say so.
The Assignment Editor is the best place to make virtual pin assignments. Click in the empty To column and on the right side a little menu will access the Node Finder. Change the filter to Pins: All, and then search away. Grab all the ones you want and then make the assignment. I recommend against making clocks(and maybe resets) into virtual pins, as they get put into the general routing fabric.