1. Download and install Zotero.*
Go to https://www.zotero.org/download/ and download Zotero for Mac, Windows, or Linux, depending on what operating system you have.
2. Download and install the Zotero Connector for your web browser.*^
3. Create a Zotero account and sign in.
*To avoid bugs and complications, make sure your browser and operating systems are up to date and running the latest versions before you download or install anything.
^If you have a pop-up blocker, especially in Firefox, you will need to turn it off temporarily while you install the Connector or manually allow a pop-up from Zotero. Zotero basically cooperates just as well with all browsers, but Google/Alphabet products, like Chrome and Google Docs, have marginally better integration if you're on the fence about which to use.
Here is a video that walks you through how to download Zotero on a PC using Google Chrome as your browser:
Here is a video that walks you through how to download Zotero on a Mac using Safari as your browser: