Summarize this article:

This is in the toolbar at the top of your screen. You may have to tap the backward-facing arrow in the top left corner of your screen to view this toolbar.    You can choose "8 hours", "1 week", or "1 year". You have successfully muted a chat on WhatsApp! To unmute the conversation manually, tap Mute again and then tap Unmute.

Summary:
Open your WhatsApp app. Tap the "Chats" tab. Tap a conversation. Tap ⋮. Tap Mute. Tap a mute time frame.