A: When creating your world, you will receive a message in the chatsaying that you received a relic in the ender chest, so you have to make an ender chest, and that way you can access your relic.
How do I get the other relics in a single-player world?
A: This question is a bit complicated. The way I found it was to open the world to LAN, but if you open the world to LAN a second time, you get duplicate relics if players join who didn't join the first time you opened the world to LAN.