Hi, my problem is i have gas (propane) to ...

The gas company should have have set and adjusted the gas pressure when they installed the new regulator. DO NOT ATTEMPTED TO LIGHT THIS WITH A LIGHTER. If this furnace has a hot surface igniter you and you lighter will be energized with 120 volts...BE CAREFUL...
If this furnace has a spark igniter you and your lighter can be lit up with up to 10,000 volts.
Since this furnace sat inoperative for so long I will bet that you have a blocked pilot assembly. Turn off the power and the gas. Carefully remove the pilot assembly. Dismantle it. Inside you will find a very small orifice Clean it out. Put every thing back together. The furnace should work.
REMEMBER PROPANE GAS IS MORE VIOLENT THAN NATURAL GAS KEEP YOUR FACE BACK AWAY WHEN IT LIGHTS IF YOU WANT TO KEEP YOUR EYEBROWS.
The clunking noise you heard was probably the gas valve trying to open.