To bid for CH you have to talk to Auctioneer, select the desired CH and give the amount of adena you want to bid for that CH.
Note: The adena needs to be in the Clan Warehouse before you can bid. The Auctioneer will take the adena from a Clan Warehouse and not from leader’s inventory.
After the successful bid you need to wait till the specified date and hour and if you are the clan with the best bid (highest amount of adena), the CH will be yours.
It is not that you do not understand, it is that you do not even question.