Endnote Online will help you to collect in one place the information you need to reference sources and assist in formatting your bibliography. This guide will show you how to use EndNote.
The AMA Manual of Style will guide you through the process of formatting your paper in AMA style. Or try the Purdue Online Writing Lab for help with other styles.
You can also use the DOI Citation Formatter from CrossRef to generate a citation for your bibliography using only the article DOI. The AMA format is listed as american-medical-association in the style list.
There are many tools on the internet to help you format your citations. The two below are other options for help with AMA style. But be aware that these sites are run by for-profit companies and have ads for paid services.