Before you can attach any cock/dildo to the fucking machine you will have to make a hole into it to fit the detachable rod that screws into the main shaft.

How you make the hole will depend on the material of your dildo.
The easiest way would be to drill a 5/8″ hole into the back of your dildo using a standard electric drill.
However, trying to drill a hole into a latex dildo can be a bit tricky because latex is very rubbery and the drill bit will not cut into the latex material properly.

The unorthodox method I used consisted in melting a hole into the back of the dildo using a conventional soldering iron.

Warnings!

• Don’t use this method unless you really have no other alternative
• Only do this outdoors or inside a very well ventilated room
• Don’t breath in the the fumes, ever!
• Have a bucket or water or fire extinguisher nearby at all times

You will need:

• latex cocks (about $15 each from a sex shop near you)
• Table vice
• Soldering iron (ideally one with heat regulator)
• Bucket of water ot fire extinguisher
• Ventilated room or outdoors

Instructions:

• Secure a soldering iron to a table vice so the tip points to the sky
• Plug the soldering iron and wait until it get hot
• Carefully slide the latex dildo into the hot soldering iron
• Keep sliding it until the soldering iron has melted its way about 3″ deep inside the dildo

If you are afraid of ruining your soldering iron you can instead use a 5″ long 1/2″ steel nail.
Just secure the nail pointing upwards into the vice.
Then use a torch to heat the nail until is hot enough to melt the latex material.
Finally, lower the back of the dildo into the hot nail so melt a hole about 3″ deep into the dildo.

There are probably better and safer methods to accomplish the same thing. If you have tried a more effective technique, please share it in the comments so I can adjust the instructions and have better advice for the future.