How to add units to cities?

I'm making a map and sure I did add units and I did make them available for all nations but then when I play tested, they weren't available in all of the cities that were in the countries which had availability to the units I made. So how do I make units available for cities to use?

Also sorry if you have no idea what I'm saying. This is my first post.

Do you have the "limit reinforcement to own country" box ticked?

If your talking about the one in the map options: no

If your talking about the one in the units tab: yes

Edit: nvm I figured it out. But thanks!