
Right, I said it was simple, so here goes.
You have two things to heat up before you apply solder. The pad and the wire.
You need to hold the two together, in place, and heat for a second or two with the iron. The bigger the pad/wire, the longer you need to heat.
With your third hand,

Try to prevent the two items from moving until the solder hardens, you'll see it go slightly dull from being very shiny.
Job done.
HTH
Cheers,
Norm.