Every link you create is automatically bi-directional. Here's the process for creating a link on iOS:
From scripture A, select some text and tap the Link button in the annotation toolbar (depending on the width of your screen, you might need to press the arrow/triangle to see additional options in the toolbar). You will see a line of text towards the top of the screen to let you know you're in linking mode. Then, navigate to scripture B and select it. You will see another toolbar pop up with the option to create the link. Tap that option.
After having created the link, next to both scripture A and scripture B you should see a link icon in the right margin. Tapping the link icon shows the scripture reference and the quoted verse(s) from the other end.
If you want to see the full chapter on the other end instead of just the linked verses, you can tap the scripture reference in the sidebar.
You can also link between other content, such as manuals or General Conference talks.
Samuel Bradshaw • If you desire to serve God, you are called to the work.