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It's the blue square icon with a white ″f″ inside. You'll usually find it on the home screen. It's at the bottom-right corner of the screen. It's toward the top of the menu, though you may have to scroll down a little to see it. Look for the green and gray storefront icon. If you don't see this option, you may have to tap See More. Marketplace will automatically display items for sale near the location you've added to your Facebook account. To change the location, tap Change next to ″Top Picks in (your city).″ A list of categories will appear. If you're searching for something in particular, tap the Search Marketplace bar at the top of the screen, type your search terms, then tap the arrow to start the search. In addition to items and vehicles, you can also browse service listings (such as plumbers and lawyers), jobs, rentals, Facebook groups for buying and selling, and selected deals of the day.  To check out items near you, tap Local Listings, then select a category to see what's available. To browse vehicles for sale, tap Vehicles, then select your desired filters (make, type, price) to see the listings. Browsing for jobs, services, and rentals is easy. Just select a category, and then refine the results using the drop-down menus at the top of the list. Details about the selected item will appear.  Swipe left on an item's main photo to see additional photos (if available). Scroll down to see a description, the set price, the item's location on the map, and information about the seller/owner. If you're browsing services, you'll have to select the type of service you're looking for (e.g., wedding planning, air conditioning services) before a list of professionals will appear. The steps to do this depend on the type of Marketplace listing:  If you're interested in an item, tap Ask for Details (below the photo). This sends a message to the seller asking if the item is still for sale. If you have a more specific question about an item or want to make an offer, tap Message to type your own message. To apply for a job, tap Apply Now. To contact a property owner about a rental or home for sale, tap Contact. If you're not sure whether you want to buy an item (or just want to save it so you can find it easily later), tap Save beneath the item's photo to bookmark it. To see your saved items, return to the main Marketplace page, tap You, and then tap Saved.

Summary:
Open Facebook on your iPhone or iPad. Tap the ≡ menu. Tap Marketplace. Set your location (optional). Tap Shop. Select a category. Tap a listing to check it out. Contact the seller or owner. Save an item for later (optional).