Tagging everyone in a Facebook group can be done in a few different ways.
The first way is to manually tag each person in the group. To do this, click on the “Post” button at the top of the group page, type in your post, and then click on the “Tag” button near the bottom. From there, type in each person's name that you'd like to tag and they will be notified when they are mentioned in the group.
The second way is to use the “Mention” button. This option is located next to the “Tag” button and it allows you to quickly tag multiple users in a group post in one click. You can select the list of people you would like to mention, enter your post, and everyone will be notified when they are mentioned.
The third way is to use the “@” symbol to mention a person in the group. This method works just like it does with tagging friends, but instead of typing in a name, you type in the @ symbol followed by the name of the group. Then, each person in the group will be notified when they are mentioned.
Finally, you can also use the “Group Tagging” feature. This feature is located next to the “Tag” and “Mention” buttons at the bottom of the post box. Here, you can quickly add all of the members in the group to a post without individually tagging each person. This is an easy way to quickly send out group notifications.
