Tap this, and you’ll find a series of ideas to help you eliminate space wasting items from your Mac, likely to include: Tap these to get more information and to find app-specific recommendations.
Here you’ll see a selection of different items (Mail, iTunes, iCloud Drive, among others). That’s interesting, but to get to the tools tap Manage. Wait a few moments, and you should see a visual representation that shows what is taking up space on your system.
Open About this Mac in the Menu and tap Storage to access these. MacOS has some really helpful built-in tools to help you boost Mac performance by getting rid of items you no longer need.