Congratulations on getting your hands on an advance copy of Pacific 1940 2nd ed!
I don’t know if the picture-posting option is available to new members (I think one needs a certain number of post counts), but it works as follows. Below the box in which you type a message, and above the Post / Preview buttons, there’s a clickable feature called Additional Options. When you click on it, an Attach box appears, plus informatin on mamimum allowable file size, plus a Browse button. The browse button allows you to select picture files from your drive. The More Attachments feature on the righ allows you to create two more attachments, for a total of three per post.
If these features don’t appear in your browser, then it’s because of the minimum-post threshold I mentioned. In that case, you might want to send a personal message to a board member who does have posting rights and arrange to email the pictures to him for reposting. I’m sure any of the people here who are eager to get a glimpse of the new game (myself included) would be happy to help in this way.