Click on the three dots of the message that you want to pin, then click on the "Pin Message".

Here, you can see that the message has been pinned.

Click on the three dots of the message that you want to unpin, then click on the "Unpin Message".

Here, you can see that the message has been unpinned.

Go to the 'My Preferenses'.
After that, the wizard will appear. Under the Chatter tab, select the 'Chatter Position: Standard (Side or Bottom)' option and click on the 'Update Preferences' button.

You can adjust the chatters width using the chatter panel.

Select the 'Chatter Position: Always' option and click on the 'Update Preferences' button.

Here, you can see that the chatter is shown at the bottom.

Tick the user's boolean and send the message..

Here, the user can see the reply option when they hover the cursor over the message, click on the reply option.

After that, the "Reply Message" wizard will appear. Enter your message and click on the "Save & Send" button.

You can see the message that was sent in the chatter.

Tick the 'Manage History' option in General Settings to start tracking chatter changes.

Your normal chatter messages and log notes, ready to be edited.

Quickly see exactly when a message was last updated with a clear time.

Click on the 'Custom edit' to change the text of any message.

Update content and click on the 'Save & Send' button.

Check the 'History' tab to see all past changes made to a message.

Untick the 'Manage History' option in General Settings.

When tracking is off, the 'History' tab stays hidden and no more changes are logged.