Yes you can put on a ring terminal to replace the post terminal that you currently have on the wire. I just did this on my boat. My recomendation to connect the ring terminal to the wire is solder it. Strip the plastic jacket back on the wire and then put on the ring terminal. Heat up the ring terminal using a blow torch. Once it is hot touch the solder to the wire and ring terminal. It should suck into the terminal and provide a solid connection. You may want to put some soldering paste inside the terminal before you heat it up. Be careful if you are doing this in the boat to make that you don't burn the carpet with drips of solder, put down some cardboard or something.