how do you change the oil and Gas of a dirt bike?

[Evlon]

I had an accident on a dirt bike and i broke my ankle for a year, within that time me nor anyone else started it and now i want to start it again, i fear that i wasted a shit load of money on it because it wont start but i want to change out all the Fuels and oils because it cant be good to just sit.... right? but i have no clue, nothing about bikes, that is probably why i broke my ankle in the first place it is a 250cc honda and i want to change the oil, and the gas, and anything else you think i should do