Tools needed
1 blow torch (heat gun not hot enough imho)
1 End cap of the correct size ( I prefare the ones with the solder ring built in)
A tub of soldering flux and some solder
Wire wool
As said in other post
Clean up pipe end with wire wool until its nice and shiney.
If your using the cap with a solder ring, slide it onto the end and heat it up until the solder can be seen round the end of the pipe / cap.
If, like me
you don't get a perfect seal first time, apply a little flux round the joint then heat it up with the blowtorch until the flux starts to run then apply the solder round the end of the cap / pipe until it runs round the pipe.
Leave it to cool on its own ................... don't squirt water on it or you may end up with a dry joint and it may leak