How to refill reserve on dirtbike?

I got a honda 100crf anf i used the reserve to get home. I'm going to buy more gasoline tomorrow. But how do I refill the reserve tank?

There's a round cap located on the top of your tank, open it.
Look down into the hole with a flashlight (move the light sided to side and no smoking).
At the bottom of your tank are TWO hoses, one sits a little higher in the tank than the other, that lower one is operated by a valve called a petcock which you have already used, it's marked R on the petcock maybe or is in that position with the turn-knob pointing up, Reserve.
Don't leave home while on it unless on the way to a fuel station.

Its in the "Same tank" Just put the fuel valve back to the normal On position, The reserve pickup is set lower than the normal pickup giving you a few more miles,.

Same tank as the main one and the reserve will fill automatically

I see you have a complete understanding of how your bike works. Just put gas in the tank the reserve will be filled.

You gotta find it first.

Reserve is just the last gas of the tank. To fill it, just fill the gas tank to the top.

There's no separate tank for reserve. In the fuel tank, you have to hose kind of things. One for main and the other for reserve. The main one sits higher, while the reserve one sits lower, closer to the bottom of the tank. Putting it onto reserve will get out as much remaining fuel as it can.