It's very simple:
When choosing the paper please make sure it’s absorbent, otherwise it will wrinkle when you wet it.
Cut the paper to size and stamp the design in the middle. Be sure to use a permanent (waterproof) ink if you’re going to make a watercolour. Of course, if you work with permanent (wax-based) pencils you can use a stamp pad containing any kind of ink.
Now colour in the design, copying our idea or varying the colours; the whole design or only part of it – it’s entirely up to you.
Then dampen the paintbrush and work over individual areas of colour. The result is a beautiful watercolour effect with soft transitions between the colours.
Be brave: experiment! You can vary the effect with different colours and using either more or less water on the brush. Try it, and you’ll see for yourself ...