The ACS Style Guide: Effective Communication of Scientific Information, 3rd Edition sets the citation style you will be using in your assignment. The style guide is available in print in the library, but you can also refer to these handy online sources:
A citation manager is a software tool that helps you organize, collect, share, and cite sources you use in your research. Zotero is a free, open source citation manager with a desktop app, browser extension, and integration with Google Docs, Microsoft Word, and LibreOffice.
1. Download Zotero. Go to Zotero.org and click on the red Download button. From the download page, download the desktop app and the browser extension, Zotero Connector.
2. Register for an account. Click on the register link in the upper right hand corner of the download page. Fill out the form to create your account.
3. Log in to Zotero. Once the Zotero desktop app downloads, find and open Preferences (Mac users: Zotero menu, PC users: Edit menu). Click over to the Sync tab and enter your username and password. Now you're set to use Zotero!
There are several ways to add items to Zotero: through the Zotero Connector, adding items manually using a form, and drag + drop a PDF into the Zotero library (Zotero will usually, but not always, extrapolate the data it needs from the PDF).
1. Zotero Connector: when the Connector notices an item to save, the icon will change to match (folder for multiple items, piece of paper for a journal article, etc.). Click on the icon and select the folder to save the item to. 
2. Manually Add an Item: In the desktop app, click on the green plus sign icon and select the type of item you'd like to add. Then fill out the information in the right hand menu.
3. Drag + Drop: Drag and drop a PDF of an article into Zotero. For most articles, Zotero will extract the information it needs and add it to the library.