I had the same issue when fitting the euro switch to my SE. From memory, I think I simply removed the terminals from the supplied molex connector and fitted them into the SE's original connectors.
The terminals have a small tab that you need to tweak out of the way before you pull the terminal out of the connector.
Just make sure you make a note of which wires go where before removing the terminals from the connectors
I also replaced the L/H switch block at the same time as my SE had the same switch block as Sheep Shagger's pic. If I hadn't done that I would have had 2 kill switches and 2 light switches (and the horn button location was really pi$$ing me off!)
Not really plug and play... But not a difficult mod either.