There are no block or lock valves on any of the cylinders so no special procedures are needed. Just connect up the hoses properly, make sure they are connected fully and operate the cylinder several times through it's full range holding for a second or two at full extension and retraction to get any air out.
When you hooked up the hoses backwards, did the cylinder operate in and out through it's full range? If not or you didn't check you could have bent the rod causing it to bind and the relief valve to kick in preventing the rod from moving.
The only hold on a cylinder is the valve block circuit being closed itself. This is one reason why it's generally a bad idea to back drag when not in float as there is no relief to any over pressure other than breaking/bending something or a hose blowing.