Depending on the browser, the console is opened differently.
To open the console in Chrome, use the keyboard shortcut: CTRL+SHIFT+J (in Windows) or CTRL+OPTION+J (in MacOS). Or, open Chrome Tools menu (icon with 3 dots on the main toolbar on the very end), then More Tools and from there Developer Tools, and when they are opened, you have Console tab. It will look like this, showing some errors and warnings:
The console shows the errors in red, and the source of the error is on the right displayed as file name where the error originated. When you hover over the file name, it shows full file URL.
Keyboard shortcode to open the console in Firefox is CTRL+SHIFT+K (in Windows) or CTRL+OPTION+K (in MacOS). Or, open Firefox Tools menu (icon with 3 lines on the main toolbar on the very end), open Developer, and when they are opened, you have Web Console.