Here's what to do:
• From the macOS Desktop, open any new Finder window
• Hit Command+F to bring up Search
• Click on "Kind" filter and select "Other", then select "File Size" from the attribute list
• Click on the second filter and choose "is greater than"
• In the third space, enter the size to search for anything greater than (ex: 100) and choose either MB or GB as the final filter
The file and app list below will automatically update as anything larger than the specified file size is found on the hard drive. Be sure that "This Mac" is selected if you're getting limited results, though you can also use the search limiters to find large files contained within single folders or user directories.
Want to use this feature to track down large files often? Click on the "Save" button in the upper right corner and you'll turn the File Size search into a Smart Folder that can be easily accessed from the sidebar for easy future retrieval, plus that folder will constantly be updated with large files only, making it a very useful way to instantly find any big item laying around on a Mac.
A common pit of enormous files is the user Downloads folder, when using the file size search don't be surprised if you run into a fair amount of .dmg and .zip files sitting idly in there that have long been forgotten.