How can I fix a tilted concrete shed footing?
Lifting it (slightly) in place may allow you access to do repairs.


If there is enough solid footing, use (2) 2x10s bolted across the studs (parallel to roof peak).  Lift both 2x10s parallel to floor (disconnect all tie downs first) using 4 bottle jacks.  Cut 4 2x4 cripples to attach to studs under 2x10 at desired final height (for safety and to backup jacks.  Leave some weight on jacks.  You shouldn't need more than an inch elevation.  
If the busted side won't allow jacking, you can run carry beams (2 2x10 bolted together) through the structure and out to each side.  Developing a footing at the jacking points may require 12" sona tube and concrete.
Mud jacking (concrete pumped under pressure) may be an option, but you'll need a pro for that.