If memory serves, you'll need to change each icon individually. Do this by pressing and holding the icon...an option should come up. There's no way to apply automatically. You'll need a third-party launcher for that.
I use Belle UI and like it alot. Once you install it on your phone, it should present itself as an option when you select a theme to apply. I did not have to do anything special or tedious such as changing each icon individually.
There's a theme setting within display or home settings (can't remember which) which you can choose it. It might not show up as the regular name though, it could be the authors name or blank.
I like to use the app Awesome icons. It is free and compatible with the stock launcher. It allows you to change each icon using any icon pack.
However, I no longer use the stock launcher. I'd recommend using Nova Launcher. There's just so much more you can do on it. You do lose the ability to use the LG widgets but I don't miss them at all. You can also search Xda forum for the thread to enable themes on the Verizon G4. I did it and it works but the number of themes is limited. The only thing cool and useful about the Smart World app/Store is the fonts you can download. The Smart World app is what is missing from the Verizon G4.
Again there's a thread on XDA to walk you through the steps to enable themes. Just a side note, I used the Any Shortcut method.