AstroPrintTM is a free service that allows you to process, store and access your 3D models in the cloud. When you upload a model to AstroPrint, it generates support material and slices the model to create G-Code for 3D printing. This code is stored in the cloud, and can be streamed to a local printer through any web enabled mobile device (laptop, iPad, cell phone, etc). This way you can have your models ready to print anywhere you go. You can also monitor your 3D printer and organize your designs in the cloud. The NIH 3D Print Exchange is integrated with AstroPrint. If you want to use the service, go to the download menu on the exchange, and click the arrow below AstroPrint icon next to the model you're interested in. You will be prompted to sign in to your AstroPrint account, and if you don't have an account, you can create one in that dialog box. Your models will be sliced and stored in your account on the AstroPrint cloud, so that you can access and print them from any device connected to the web
Additional support can be found in the AstroPrint FAQs.