If you need to access the folder 'Library' - you cannot do that by navigating to it in Finder.
The easiest way is to open 'Finder' application and click on 'Go' in the context menu, then select 'Go To Folder'.
In the appeared spotlight menu, enter this path:
~/Library/
Then, hit on Enter/Return key, and the hidden Library folder will be opened.
Please note, macOS has several Library folders.
1) User Library folder. In the path, shortcut ~/ represents the path of /Users/Your Profile Name/. By entering ~/Library - you will open User's library.
2) System Library folder. To get to the System Library folder, you need to go back to Go To Folder prompt, and enter this path instead:
/Library/
Then hit Return key.