Create a new topic in Google Groups

Watch How to Create a New Post in Google Groups:

When you create a new topic you also create the first post in the topic. 

To create a new topic via email for an email list, simply email the group like you normally do.

To create a new topic in a forum:

1. At the top right of the group’s Topics page, click the red NEW TOPIC or POST A QUESTION button. The button you see depends on the type of the group.
   
2. Type your Subject or Question title, depending on which you’re asked for.
   
3. Based on the type of group and your group permissions, you might see an option to select the type of post.
   
   For example, you might see this in a Q&A forum:
   
   
   
   Here are the possible options you might see:
   
1. Discussion () - This creates a general discussion topic. If you clicked NEW TOPIC and don’t see any other options, you’re starting a discussion.
2. Question () - This creates a new question in a Q&A forum. If you clicked POST A QUESTION and don’t see any other options, your topic will automatically be a question.
3. Announcement ()- This creates a topic containing important information. All members of the group can read announcements, but typically only group owners or managers can create them.

4. If you see a Display at the top checkbox (like in the picture above), check that if you want to create the new topic at the top of the topic list. It will be “sticky” and stay at the top. Sticky topics show a pin () in the standard Topics view. This option is available only for authorized users.
   
   Authorized users might also see a Lock checkbox. Select this if you want to block members from replying to the topic. This might be useful if you’re creating an announcement.
   
5. Click Attach a file if you want to attach a file to the initial post.
   
   In the Select a file dialog box that appears:
   
1. Click the Choose files to upload button.
2. Navigate to your file.
3. Click the Open button. The file is uploaded to Google Groups.
   
6. Type the content for the topic. You can add formatting with the buttons above the topic body.
   
7. Depending on how your group was set up, you might see an option to add tags to your topic. Tags are used to categorize and find topics, and are commonly used in a Collaborative Inbox. Tags are enabled and created by whoever manages your group.
   
   If you have this option, click the suggested tags (at the bottom, in blue) that you want to add to the topic. Tags appear in the Tags field as they are added. For example, the “service” tag was added here:
   
   
   
   Or, start typing a tag in the Tags field. If a tag exists that matches what you’re typing, you’ll see the tag. You can then press the Enter or return key to select it:
   
   
   
   Tip: There might be tags available to you other than the ones shown in the suggested tags list. If you know the tag you want, just start typing it. Click the Tags button back on the group’s Topics page to see the complete list.
   
   Note that the maximum number of tags a topic can have is controlled by the group owner. See Manage the topics in a group to learn more about using tags.
   

8. Click the Post button to post the topic. The topic appears in the list of topics for the group.

Reference:  Using Google Groups for Business -  Post to a group