To temporarily reveal the ~/Library folder you need to do the following;
- Open Finder and on the menu bar, at the top, select Go to reveal the drop-down menu.
- Hold down the Option key (marked ALT) and you will see the ~/Library folder appear.
- You may now select this ~/Library folder with your mouse or trackpad.
- As soon as you release the Option key, the ~/Library folder will be hidden once more.