You need your map in digital format so you need to scan it or take a digi photo of it.
When you make a post you will see that you may have a button saying "Go Advanced" that depends on whether you have set your profile to post with the simple or advanced layout. Anyway, there should be a button saying "Manage Attachments". When you hit that you get a panel of all of your uploaded files so far. Top right is a button for the upload called "Add Files" where it asks you to find the file on your drive with a "Browse" button (or may be something slightly different on a Mac). When selected it will upload it and show the thumbnail in the bottom panel. You can arrange your attachments there. When done there is a "Done" button and then it goes back to your text box post message but it should list in text the files you uploaded. You can attach the files inline or not. If inline then they appear in the middle of your text, if not then they are at the end. Normally you see the images as thumbnails which come up in a "light box" which is a smaller window. If you click thorugh that then it should come up full image size.
You can inline hosted content into your post with the usual BB code. So like most forums ours would be (and of course how I am gonig to type this without it interpreting the code....)
Code:
[ img ] https://www.cartographersguild.com/images/cartographer/misc/cartographer_logo_short.png [ /img ]
Without the spaces in it above would then produce this:
![](https://www.cartographersguild.com/images/cartographer/misc/cartographer_logo_short.png)
If possible tho, please use a smallish image for that. If you inline external images which are huge they come out huge here too.
Below is an example of the attachments in a lightbox.