wa alaykkum assalaam wa rahmatullahi wa barakaatuh
In the text editor,
There are three command button at the bottom right corner. The middle one is "Upload a File". Click on that one.
Select the picture you want to upload and click 'open' in the dialog box.
Wait till the pic is uploaded and Click on the 'Full Image' button that appears after the upload.
Your picture will be uploaded and embedded in your post.