If you don't want to sync v1 and v2

The easiest way to start using your existing OmniFocus database in OmniFocus 2 is probably to sync. But, if you’re not syncing your OmniFocus database, here’s how to copy your database manually:

  1. In OmniFocus 1, Command-click on the main window’s title. This opens
    a little drop-down. Select that top folder named OmniFocus. This
    will open a Finder window with your OmniFocus v1 database in it.
  2. Repeat step 1 in OmniFocus 2.
  3. Quit OmniFocus 2.
  4. Copy the file found in step 1 to the location found in step 2.
  5. Launch OmniFocus 2.