TitleDB is something that is completely unrelated to the current topic, but to summarise, it lets you scan a QR code with FBI to install homebrew CIAs automatically through the internet. It doesn't sound like something you'll need to use.
If your HBL on the home menu still isn't working but you still want to use it, try opening the Rosalina menu (L + Down + Select) and going to miscellaneous options. It should say "switch the hb. title to hblauncher_loader" or something like that. If you press it, it should cause the homebrew launcher on your home screen to start working.