How do I remove other participants from a conversation? 

You cannot remove anyone from a direct conversation. However, you can remove others from conversations with a subject if you are the admin/creator of those conversations. 

• Open the conversation you would like to edit
• On the top bar, tap the subject of the conversations (above where it shows the number of participants)
  
• The Conversation Details page should automatically open 
• Below the 'Participants' heading, scroll through the people in the conversation until you found the person you would like to remove
• Once you have found that person,
• For iOS: tap and hold to display the 'Remove' button
• For Android: swipe left to display the 'Remove' button
• Tap that red 'Remove' button and then tap 'Ok' on the pop-up window to finalize removing this participant from the conversation