I have an open office data file on a flash drive how do I get into open office on my mac

Drag and drop it onto your Desktop. Control-right-click on it, and select OpenOffice from the Open With menu items.

Assumption: You have enabled √ External disks in Finder Preferences : General so that you can actually see the mounted USB stick.

Look in Finder Preferences : General. Check as shown, though you may not need the last two:

If your USB stick appears, then drag the OpenOffice file to your Desktop as I suggested earlier. If not, from the menu, select Logout, and sign back in. Reinsert the USB stick. It should appear on your Desktop.