Be wary about following the instructions on that particular page, it's one person's hacking efforts (note that XDA Developers did close that thread)
But regarding the OP's query, keep in mind that JP5 tablets are specifically intended to be used within a correctional facility's control and oversight. The installed custom Android OS used in JP tablets is restricted and limited so the tablet itself is by design going to involve a lot of content filtering and apps having limitations to various online services. The thing is, unless JPay releases a typical, common usage version of Android for your JP5 (not going to happen), your options to upgrade this tablet to newer version of the Android OS isn't likely. On top of that, the JP5 tablet is very dated and will have complications using modern day online services anyway -- it's just a software being out of date matter but the hardware is just too old too.
I'll suggest instead of fighting with your JP5 tablet to be fully functional in a current setting that you just start looking into buying a new, more capable phone or tablet. There are a lot of options to choose from now. If budget is a primary factor, an Amazon Fire HD8 tablet is only $90. It's going to be running Amazon's FireOS and include a lot of Amazon branding but as a basic tablet a good value.