Ive been told i need to drain the caburettor, and im useless with engines. i just need a guide. my bike is a rieju rs2 125 matrix. Thanks mike.

Most carbs have a drain screw at the bottom of the bowl (the bowl-shaped bottom of the carb body). On my older motorcycles, this has always been a brass drain plug that's clearly a different color from the silver-colored carb body and bowl.
Some carbs also have a rubber hose leading down from the carb body or carb bowl. Gasoline may drain out of them when you loosen the drain plug. However, taking out the drain plug should let the gasoline dribble right out of there. Keep an absorbent rag or small can/jar/cup to catch the gas that comes out. Avoid plastic, especially styrofoam, containers, as gasoline will dissolve some plastics, creating a gooey, nasty mess.
If you are having trouble finding your carb, trace the path of air. You can start at the end, with the tailpipe, and work backwards through the engine to the carbs. Or, you can start with the air filter, which is probably directly attached to your carburetor.
Good luck!