When an update becomes available you will see a notice of an update under the Plugins tab in your WordPress dashboard and under the Dashboard tab as shown here:
Clicking on either of those two links will redirect you to the update page. Click 'Start Update' to run the update:
In some rare cases, the update process is not compatible with some server environments. If you find that you are unable to run the update, please follow these instructions carefully! This will not affect your content or the galleries you have created.
Deactivate NextGEN Pro/Plus and then delete NextGEN Pro/Plus ... No need to NextGEN Gallery. Log into your members area at https://www.imagely.com/ and download the current version of NextGEN Pro/Plus. The link to download is listed at the top of the page content.
-- Install the NextGEN Pro/Plus plugin via the WordPress Dashboard.
-- Log into your WordPress Dashboard. Go to Plugins > Add New ... click on Upload
-- Browse to where you saved the zip file you downloaded (see above). Select, install, activate ... and you should be good to go.
Feel free to check your settings, just in case, but all should be as it was. If you are still have problems, or are unable to access your members area then by all means let us know.