Basically, you go to any petrol pump.
There will be 2-5 pumps, and some are labeled" Diesel" and "Petrol"
For petrol, just follow the bikes. best guidance. Wait in line, if it takes too long, start pushing in, since "Queue" "Patience" is not a word in Pakistani mentality. Tell the pump operator amount of fuel. If you don't care about mileage, just get it done in Rupees, not litres.
1)Find a reputable pump. Ask around
2)Locate the petrol dispenser
3)When it's your turn, open fuel cap and tell him amount" 100 rupees, 1 litre" etc.
4)Make sure the meter is reversed to O
5)When finished, close cap, make sure it is closed
Enjoy the trip:)