Most items sold here are for delivery, but if the ad states that something is for collection the seller can send you their address once you have paid through eBay's checkout. (eBay des not allow members to disclose contact details until after the item has been paid paid for.)
Remember that if you want the protection of eBay's money back guarantee, you must collect it in person. eBay will send you a collection code that you must give to the seller as proof that the item has been collected.
If you arrange your own courier, the purchase becomes ineligible for eBay's money back guarantee. You would also have to get the courier to take the collection code, if the will, or get it to the seller some other way.