There are some initial explanations here.
When you open the site for the first time you should see some little green tutorial cards that point to some basic features, like search, play, settings etc. In case you have skipped them you can activate them again in settings 
> general.
SC-Voice also has a section “sutta study with SC-Voice” in it’s own wiki where you can find more detailed instructions (but alas! they still need to be adapted with the latest play options that have been added).
If you have more specific questions, please ask, and I will answer as I can.