Some help? (Computer savvy people please!)

Ok so i was trying to create a motivational poster. I made a collage on a ppt slide and then saved it in interchange format (jpeg). I then tried uploading it onto the motivational poster site but the final product cuts off part of the top, boven and bottom of the collage picture. I tried shrinking the foto in picture manager but then when i uploaden it again to the website, the foto is just in worse quality and its still cut off.

Does anyone know how to resize the ppt slide picture so that it will fit properly? Unfortunately, i dont have photoshop...:(