Red curry paste is a paste made mainly from chilli, cumin, galangal root and onion. In Thailand we buy it, we don't make it, just like you buy mustard rather than make it from mustard seeds. The best paste is finely ground in a Thai mortar and takes several hours to prepare, so I would strongly recommend you find an Asian grocer who stocks it, or ask your local supermarket if they can get hold of it.
I confess I've never made this paste myself, the following is my mothers recipe, she loves using Mono-sodium Glutamate, but its use is optional.
4 Tablespoons Dried Flaked Chillies
30gms Chopped Onions
1 Tablspoon Chopped Galangal Root
4 Cloves Garlic
2 Tablespoons Chopped Lemon Grass
1 Coriander Root, Chopped
1 Teaspoon Ground Cumin
1 Teaspoon Peppercorns
1/2 Teaspoon Salt
1 Teaspoon Coriander Seeds (or ground Coriander Seeds)
1 Teaspoon Kapi Shrimp Paste (optional)
A pinch of Monosodium Glutamate (optional)
1. Place everything into a Thai mortar.
2. Pulp until all the ingredients form a fine paste.
3. If the mixture is too dry add a teaspoon of oil to loosen it.