Hi Charlie,
- To translate page, you have to clone content of Page - then translate all texts inside.
- If we talk about SP Page Builder component itself - you have to translate english .ini files:
- administrator\language\en-GB\en-GB.com_sppagebuilder.ini
- language\en-GB\en-GB.com_sppagebuilder.ini
Of course you have to change language file prefix to your country native one, like always in Joomla.
You can take some already translated phrases from SPPB 3.x translation files, so it will speed up your work.
Now all is in your hands (& keyboard)!