Do you mean it's not showing on the item you have already listed, that is, those sneakers, or for items you are yet to list and Collection is not showing ?
If for the sneakers, you can revise that postage / delivery detail.
Preferably use a laptop / PC if revising is causing an issue on the app or mobile browser, click on Revise item in the active listing, scroll down to delivery details and amend to Collection only.
One more tip, it's a very expensive item, hopefully you are successful in making this a collection only, and remember not to hand over the item when sold and paid for, until the buyer gives you the collection code. I would also enter / scan the code in their presence, to ensure it is correct , as it's your only proof of collection.
@ursulgreenslad_0