Rocket Fuel is a necessary resource if you wish to run your Spaceship. To make Rocket Fuel, you'll want to process Crude Oil through a Refinery. (You may also use Buildcraft Fuel -- they are currently interchangeable)
For buildcraft fuel make a buildcraft refinery and power it to make the fuel.
for galacticraft fuel place a canister in a refinery and fill the refinery with oil then power it.
Both refineries, oil and fuels are interchangable i believe.