I apologize if this has been covered,but does anyone know if there is a way to use the WB in Bunker Hill?

Complete a certain part of the main quest. It'll make sense once you get to it.

Yes there is a way to get access to the workshop although you can't build a lot there.

i've got 25 settlers a few shops, some defence, water and crops.

I don't know about that - I built an upper balcony that wraps around the central trading area, and placed a mortar on the roof of that building. Granted, the on-the-ground space is pretty limited, but with the upper balcony set-up, I was able to place missile batteries that can nuke anyone who gets near the area.