Wire brush everything to get the rust off, check that all the parts are able to move and are not rusted together, repaint and buy a high lift rebuild kit .
Thats not a HiLift, its a JackAll. Spares are not the same, Otherwise same operation as HiLift.
Clean it up & oil its rubbing bits. Use it.
Be careful with it. If unloaded, its carriage may unexpectedly drop and if loaded, stay clear of the handle, it can clobber you if you are unaware of how the jack works.
I am sure YouTubes abundant of their operation.