Dear Bruce,
Is it necessary to install the update? I would say yes, because updates serve a purpose, often additional options, compatibility or bugfixes.
How to get your hands on the update? Please have a look at the documentation of the plug-in. The documentation is included in the original download/install package.
Or alternatively, you may look here www.innato.nl/index.php?option=com_kunen...10&id=307&Itemid=412 or here www.innato.nl/docs/manuals_softw/DOCUMEN...lone_trl_plg_j30.pdf The latter is a manual, see page 2 under "How to check for updates".
Good luck!

I purchased Login One Premium in January this year. I have version 2.50 installed, and I am using Joomla 3.7.4.

I see that the latest version of Login One Premium is 2.6.4.

Is it necessary to install this update, and if so, how does one get hold of it?

Thank you
Bruce