Save your images from your phone or camera to your computer – the smart thing to do is to put them in a folder describing the image. Note the names of your images – these need to be changed too – Use a name that groups them together and orders them. See next grab.
So now they are organized and named to help you keep track of them on the server you need to consider the size of them – these are only about 1.5mb off my iphone but an slr image can be 10-20mb easily – UPLOAD SIZE LIMIT for wordpress is 8mb so if they are more than & you need to size them first.
Your site is set up to automatically create the right size BUT some large images are sometimes too big. Use the site http://www.befunky.com to make an image 2000 pixels wide and the upload will adjust the final size and the dpi for you.