The example shown below is the progress indicator for a photo that is being uploaded.  (This instruction jumps ahead a little and assumes you know the basics.  Read "Getting Started" below for basics.)
Large full size photos take more time to upload than smaller photos - this is due to your camera setting.
The example shown is using the Google Chrome browser.  Internet Explorer, FireFox or other browsers may differ in how they display uploading progress.  

You can reduce photo sizes by two methods.
One is to adjust your camera settings to record smaller photos.  This will result in faster load times but reduced photo quality.
Second is to process the images in software such as PhotoShop Elements on your computer or online software such as http://www.picresize.com/

Okay, you either want to "reply" to a post, or you want to start a new thread topic.  Click the appropriate button.

Firstly, you have to know where your photo file is located on your computer.  Then click the "Choose file" button shown below.  A screen opens up for you to pick the photo file on your computer.  Click your photo that you wish to upload.

Okay, so you picked your photo, clicked "Add Attachment" and now you can see that your photo file is added.  If the photo did not upload, you won't see change - probably because the photo size is too large.  Make a smaller copy of your photo if that's the case.

If your done with the message writing part, you can simply click the "Post" button.
Your photo will show as an attachment at the bottom of the text - the photo is a thumbnail (reduced size) about 500 pixels wide.  If someone clicks on the photo, it will enlarge to full size in a new window.

You may have noticed the "Insert Into Post" button.  This button will put the photo thumbnail within the message body.  As many as ten images can be posted in one message.

Note: the photo will appear as a sort of placeholder code - but will show the photo thumbnail when viewed. 

After the "Post" button is clicked, the image is located within the message.  You won't see the image until after posting.  You will see the image placeholder - in this illustration below, it's [attachment=367]

Each uploaded image is assigned an attachment number.  Multiple images will appear as [attachment=368] [attachment=369] [attachment=370], etc.

You can cut & past attachment numbers and place them within the message body at will.  Use the "Preview" button to see the final effect.