If you've got the molds it is not hard at all. I find the isomalt beads are easier to work with. Melt them and add some food colouring (green for emeralds, red for rubies, etc). Melt them in the microwave in short bursts on lower power.
If you have some silicone muffin cups these work great for melting the isomalt. You can then use them to pour the liquid isomalt into the molds. They're not too big so you don't melt tons of isomalt that you may not need. If the isomalt sets, break it up and re-melt it.
Just be careful that you don't touch the liquid isomalt...it is very hot and you can burn yourself.