jazzman34653 was trying to post a pic in The Perfect Straightgrain forum and couldn't. Claimed it didn't work because of his OS. I typed this up in response and directed him here.
Posting pictures shouldn't have anything to do with what OS you are using. You have to host the picture online, not on your computer.
You should have online filespace available through your internet provider. This is usually advertised as being space for hosting a web page but it doesn't have to be used that way. You just upload your pictures there. Contact your ISP to find out how to upload files into your filespace.
So, here's a pic of a Ser Jacopo pipe that I own. The picture is actually stored on a server somewhere. Don't know where, but the url is this:
To add this picture to this message, I added a TAG from the toolbar above the edit window while I was creating this message. The tool itself is the first on the left and on the bottom row.
So I clicked it, and pasted the url of the online picture into the resulting dialog.
Viola! The picture appears in the message.
I use a Mac running OS X. The program that I personally use to upload pics to my filespace is called Transmit and is a shareware FTP utility. It costs something like $10.
You could also store your pictures at mac.com or on another service such as photobucket.com.
Hope this helped...