1. Open your inventory by tapping on the "Inventory" icon in the lower-left corner of the screen.
2. Select the first item you want to combine by tapping on it once.
3. Hold your finger down on the selected item and drag it over the second item you want to combine it with.
4. Release your finger when the items are overlapping. The items will automatically combine, and the resulting item will appear in your inventory.
You can also combine items by tapping on the "Combine" icon in the lower-right corner of the inventory screen. This will bring up a list of all the items in your inventory that can be combined. Tap on the two items you want to combine, and they will automatically combine.