Above ground pool drainage....

[matt4x4]

Connect your manual vac head to the hose, connect that to your skimmer as usual, place the multiport valve to backwash or drain (preferralby drain, but do backwash for a good half hour to help clean you filter out well).
Just make sure you don't let the pump run dry.
Please rememeber that if you liner is over 1 year old, it will need replacing before refilling the pool, yes, the pool may fill, but it will rip in a matter of weeks at best.
The only time I've seen a liner live through a complete draining was when the liner was less than a season old and still retained it's elastic properties.