Congratulations, a lot of fun and hard work to come.

The most important thing is to evaluate the truck and determine exactly what it is going to need.

If your ignition switch has a little handle at the bottom, look at the key opening. If it is vertical or to the right, try turning it. These switches can work without keys, vertical is off, to the right is on. With a key in, turn to left and remove to lock.

Evaluating the engine is the first priority. forget about the gas tank.
1. remove the spark plugs (mark wires) and spray a lot of WD-40 or similar into each cylinder and let it set.
2. clean the battery terminals. If you live in a place where it freezes in the winter and it wasn't in a heated garage the battery is junk. borrow one from something else or buy one.
3. drain and refill the oil.
4. check the coolant. if it is empty, fill it slowly and have a pan ready to find the leak.
5. remove the air filter and disconnect the gas line from the carb. and stick the end in a bottle.
6. key off, spark plugs out, some rags on the inner fender to catch the oil from the plug holes, crank the starter. if it turns over, crank until you see the oil pressure gauge move.
If it doesn't turn, try to move the engine by hand. If it doesn't move, engine is frozen.
7. put the plugs back in (clean), clean the points with some 400 sand paper or points file, pour a little gas down the carb, key on and see if it fires.

If it does go have a beer, it's a great day.