Can Gmailmessage have an attached file?

hi, I am wondering if a gmaimessage can have an attachment. If yes, how to get a file attached?

Did you check the GMailDemo? There is a big button "Select File to Attach" with the code assigned to the OnClick event handler to attach a file to an email:

  if OpenDialog1.Execute then
    AdvGMail1.Files.Add.FileName := OpenDialog1.FileName;
    btnAttachFile.Caption := 'Added: ' + OpenDialog1.FileName;
    lstFiles.AddItem(OpenDialog1.FileName, AdvGMail1.Files[AdvGMail1.Files.Count - 1]);
    lstFiles.ItemIndex := lstFiles.Count - 1;
    btnRemove.Enabled := True;

That is helpful! I will try that later.
I have a registration for google drive, can I use the same credential for gmail?

I don't know, I had a gmail account before getting a google drive account. I'd suggest to first try to get google mail via the web working for you and then try to access it with our component.

When I use gmaimessage, it doesn't have any place to put in my gmail account information. Do I need some other component to support it?

I have it working now with that TMSFMXCloudGMail component. when I attached a file, it seems that a file size limit applies. The file size can not exceed 300k. Otherwise, I got AV. I am wondering if there is a work around? I need to send images. A typical image size is about 3-5M.

This issue has now been fixed.
The update will be available with the next release of the TMS Cloud Pack for FireMonkey.