can anyone tell me how in blazes you post a pic? if i click on 'insert image'

i dont know what or HOW to insert something there. if i drag a file it wont let me in the box but outside the box i can and i then see just the image and then when i click 'back button' it has erased all text and no pic. there is nothing explaining how to do this. what am i doing wrong? (all pics are Jpeg and under 60KB) clicking the 'insert image' doesn't give me a new window to choose a pic, cant drag one over, cant copy and paste one in there, clicking on [img] doesn't do anything...what am i missing?? PLEASE HELP.