Go to your Notifications tab
Tap the gear icon
Tap Muted, then tap Muted words.
Type in the word or hashtag you’d like to mute. Entries can only be added one a time.
Select whether to enable this in Home timeline or Notifications, or both.
Select whether this is From anyone or From people you don’t follow (for enabled notifications only).
Tap For how long? and choose between Forever, 24 hours, 7 days, or 30 days.
You will see the mute time period indicated next to each entered word or hashtag.
Tap Done to exit.