12V blade fuse box type of connectors - identification
These are known as Faston (that's a trademark), tab, quick disconnect, spade or blade terminals.  These are all names for the same thing, but there are different sizes - make sure you have the right tab width and thickness. These are probably 1/4" wide and 0.8mm thick. You want a matching female connector, and these are normally joined to wire by crimping.

The associated terminals normally come in three wire sizes, with red (small), blue, and yellow (large) insulation. They cost pennies, and you can buy assortment kits. Make sure you have the right size for the wire you're using, or it won't stay put.  Really, you ought to crimp it on with a special tool costing £10-100 depending on quality. You can do it with pliers, but its very hard to make it reliable.