Earlier I wrote about the User Theme Extension to change the theme of Gnome Shell. Then I reported you should manually installing GTK themes in Gnome Shell due to the css bug. But with the fix css extension, you can now use the User Theme Extension again.
Open the Gnome Tweak Tool.
Under Shell, click the button to browse for a Gnome Shell theme zip to install.
It will say if it was successful.
To apply the theme, either select it from the dropdown menu…
or from the User Theme extension. (I recommend that method)
Tip: When installing extra themes to the User Theme extension, you can run out of room. Press Alt + F2 and run this command to make room:
sed -i ‘s/let numColumns = 3/let numColumns = 6/’ ~/.firstname.lastname@example.org/extension.js
This is the before image. The image above is the after.