Connecting to a 12v Power Supply

12 volts come from a battery or from a mains adapter.

The battery may be charged from the mains, a vehicle's alternator, solar panels or a wind turbine.

If you want to know more about 12v batteries, you should visit here.

Mains Adapter

If you are using a mains powered 12v adapter then you can either cut the small plug off at the end of the adapter wire and 'bodge' your own connection or you can get hold of a socket to plug the adapter into.

With the Power Plug Socket...

See Fitting a Power Socket for more detail... or...

Bodge the Adapter...

Cut the plug off the end of the wire furthest from the body of the adapter, to give yourself as much spare wire to play with as possible. But its always sensible to leave 10cm of wire connected to the plug in case you want to use it later.
Bare & Twist the cut ends then either:
Twist join them to your circuit wires, check they are connected correctly, solder then insulate (for a permanent join), OR
Use 2 sections of a connector block and join the adapter wires into the female side and the LED circuit wires into the male (for an adaptable, easy connect join), OR
Use 2 sections of terminal block for a semi-permanent join.

If you are Connecting to 12 Volts...

Your options will most likely be...

Soldering or using terminal blocks to connect to wiring that already exists (you should be familiar with the electrics you are going to use);
Using Big Crocodile Clips to connect direct to the battery terminals;
Using Small Croc Clips to attach to small contacts inside old light fittings;
Using a Car Plug to fit into a cigarette lighter socket.

The Car Plug is the most elegant and you can see how to wire it up here.

Solder your wires direct to Mini-Croc Clips or screw your wires to Big Croc Clips.
Remember, LEDs only let electricity flow in one direction - but won't be damaged if you connect them backwards; Just fit your croc clips and swap the terminals you connect them to if the circuit doesn't light up.