First of all you need to download Stockimo from AppStore. Once you download it, sign up on Stockimo, its free to join. After you have signed up, Log in to your account and upload your photos by clicking on upload button. Select the photo which you want to upload. You can also upload photos taken in other apps like Instagram, Hipstamatic, Snapseed.
After you have selected your photo, Give it a title and add tags to it so that people can find it. Be as relevant as possible, Buyers use tags to find photos. Once you complete all this, Click next and follow all steps and click on done to upload photo.
Once you upload photo, your photo will be reviewed by Alamy reviewers and will be accepted if it score more than 2 out of 4. if your photo do not score more than 2, It will be rejected. Once your photo is accepted it will go online for sale. You will be notified whenever it gets sold. You can get 20% to 40% royalty for your photos.