Tap on the coin / stock to open it.
Tap on the star in the top right to stop following.
If you are following multiple pairs for a cryptocurrency, "un-starring" the coin will remove all followed pairs from the list. If you wish to only unfollow particular pairs, see steps below:
Open the followed asset from the Following screen
Tap on the price source (exchange and pair) above the price chart.
Un-star or star specific pairs that you wish to unfollow or follow, respectively.