If you push arm into side of seat while turning arm backwards it will release from chair. You can then unzip bottom and carefully start to remove the foam padding which contains the metal height adjustment assembly. Mine was cracked and rewelding it in correct position solved the problem. Then reassmble and reverse procedure to install on seat. Winnie also sells new metal assembly for I think about $60. Parts list on web shows item #.
2005 Itasca Meridian 39F, 2005 Grand Cherokee, Blue Ox Adventa tow bar, US Gear Brake system
2 Boxers, "Gidget" & "Butch"