I think if it was me id be cutting them, putting individual connectors on and connecting them to the corresponding wires. It’s probably the easiest way.
The easiest way would be the red spade connectors, get the covered ones which will keep the weather out a bit better. You can get them on eBay or you could nip to Halfords and they’ll have them in smaller quantities.
Have a look on YouTube if your not sure on how to use them. But it’s straight forward. Cut the plugs off, strip some wire, put the connectors on and plug them in.