Hi,
Unfortunately there's no way to use this extension without using the Meta Box plugin to register meta boxes.
If you're using normal way to register meta boxes as shown in the Codex, you have to write your callback to output the meta box and its content. Thus, everything must be done manually.
If you use the Meta Box plugin, it handles all that work for you, meaning the output of each custom field in the meta box is handled. And only that way, the "Tabs" extension can join the game, e.g. it can help you to change the output to organise fields in tabs.
So, briefly, if you want to show fields in tabs, please install and use the Meta Box plugin first, then follow the documentation of "Tabs" extension to show fields in tabs.
Thank you.