I need some advice on working out.?

Basically, I'm fairly skinny but not so much that you can spot any bones 'sticking out'. Recently I've begun to put on weight in order to build muscle, but currently I only have two 5kg dumbbells and I really have no idea what to do in terms of exercise and diet. I have no money for the gym or other equipment so how often should I work out and what should I do to notice a difference in my body.