Hi robo,
before trying to post on the forum it is best to check the size of the photos that you wish to post, often they may be up to 4mb and too large to upload.
I use Paint to resize pictures and click on resize then click the Pixels button and enter 800 X 600, the result is a pic that can be easily uploaded
.
Below the posting area is a button to attach, click on it and locations will appear on your computer where your pics are stored, Select the pic and click on open.
Information will appear showing the status of the upload and when uploaded will be the option to remove or insert. Click on the insert button and a pop up will appear asking it you want the pic to appear in the text. I usually want the pic to appear on the page not just as a small icon so I use the option to insert into the text.

Having said that I use Chrome as a browser and Apple will not be the same in the finer points.

Just have a go.

John

If you are using Picasa choose your photos, then export them to the Pictures folder, they will be in Picasa export folder filed in the folder you have named, they will be resized for you on the way to the export file you can then load these photos into your post
Cheers
David