Go into your Library as stated earlier and try that.
If this fails, install AppCleaner (3rd party app that gets rid of remnants...like Revo Uninstaller for PC's). In Macs, you can't just drag and drop into the trash. Once you download and install AppCleaner, drag from Applications Avast into over the AppCleaner icon, which I suggest you put on your desktop. A window will open up that will contain all registries and everything related to what you want to delete. Click on delete and it's gone into your trash bin.
They now make CCleaner for Macs, and I recommend it to thoroughly delete items since the Apple trash removal is not as thorough. It takes longer, but it's worth it and decrypts it.
I've used AppCleaner for getting rid of other software and it's recommended by other devs., and best of all, it's free.
I'm not sure Avast recommends it, but it works for stubborn software that you can't remove.