Need help with steering gearbox

[SS68]

Last week my gear box started leaking. so i looked around and bought a rebuilt one from the local napa for around $140 with an $80 core. Now onto the problem, I put it in today but now the truck feels like it has no power steering at all i open the pressure line going into the gearbox and it shoots out fluid. i open the return line and also fluid shoots out. what am i forgetting to do? i lifted up the front end and turn the wheel both sides check fluid level and its full. but once i put it back on the ground its hard to turn. Anybody have any suggestions?