You may be confused about how to access the SIM card on the Apple iPhone 4. Follow these steps and you’ll easily figure it out.
1. Grab the SIM eject tool that came with your iPhone. If you don’t have it, a paper clip will also work.
2. On the right side of the phone, there is a slot. Insert the eject tool (included with the iPhone) or a paper clip into the eject hole in that slot.
3. The tray should eject, where you can insert or remove the SIM card as desired.
Image source: Kawa0310’s Flickr photostream