- Click on the Apple menu, select App Store. (If it’s not in your Apple menu then you can find it in your Applications folder too.)
- When the App Store opens click the Featured button on the left end of the top row.
- Typically there is a big ad for the current version of the Mac operating system (macOS) such as OS X Capitan or macOS Mojave. If prompted, enter your AppleID password. Sit and wait for the download to complete. The speed of your Internet connection will affect how long it takes. When the download finishes an app named “Install macOS” will open. You can either start the install immediately or quit it and do Stage 2 in the future.
- When you’re ready do this:
- Go to your Applications folder and find the Install OS X El Capitan application.
- Double click it and follow the prompts to let it run.
- You’ll be asked to enter your Mac user account password early on.
- Once the install starts you won’t be able to do any other work on the Mac. Just let it run. It’ll take about 45 minutes or so to finish. It’ll restart your Mac when it’s done.
After your Mac restarts, login to your user account. Depending upon which features you already use, you’ll likely be prompted with a couple of on-screen questions. As a precaution, I recommend that you do not enable any of these features that you are asked about.