In order to post photos on MiceChat, you will need the help of one of the free photo hosting services. I use PhotoBucket, so while other services are similar, I'm explain the service I'm familiar with.
PhotoBucket is very straightforward as to uploading your photos, creating albums, and the like. If you have problems, they have some of the best tutorials I've seen, but I doubt you'll need to refer to them.
Once you are uploaded, you need to start your new post on MiceChat.
To post your photos, you'll need to have two windows open. One to MC where you are creating your post, and the other open to PhotoBucket, on the album where your desired photos are.
Starting at the PhotoBucket page, hover over the photo you wish to insert. Four codes will appear under the photo. Click on the bottom one, the IMG file. Copy that code. Return to your MC page and click on where you wish to insert your photo. Do not use any of the tools at the top of your window. You are just going to click your cursor on the insertion point, and then paste. Your photo image info will appear there. Then go to the bottom of your post composition window, and click on "Preview Post". Your post, so far, including (hopefully) the photo you just inserted will be displayed for your review.