The picture is the terminal block for the headlight and parking lights. From your description it doesn’t seem like you have a relay. The existing horn won't work with the horn button on the steering wheel without a relay. Plus a relay is a much safer way to wire the horn.
You can buy a relay from Classic parts.
https://www.classicparts.com/1947-54-Horn-Relay/productinfo/53%2D311/Wire it in accordance with the diagram in this picture. Six volt and twelve volt systems are wired the same.
I have a twelve volt system and used 12 gauge wire to supply voltage to the relay. I suggest getting this power from the fuse panel that the existing horn button is wired to. Use a 10 amp fuse in the panel and run a 12 gauge wire to the “B“ terminal on the relay. The wire coming from the Horn should also be 12 gauge and that will go to “H” terminal labeled “H” on the relay. The remaining terminal labeled “S” goes the the wire coming out of the steering wheel. That should be at least 16 gauge and soldering that wire on to the existing wire is fine. Do use heat shrink.
The relay can be mounted anywhere that is convenient. The factory position on my ‘52 shares the mounting bolts for the brake and tail fuse holder mounted on the drivers side firewall.
