If you have successfully downloaded the lightfolio.lrplugin zip file (instructions found here https://www.lightfolio.com/help/lightroom-plugin), let's set up the rest inside Lightroom. The plugin is a Publish Service, so keep that in mind as we go through the following steps:
(1) Go to File and select Plug-in Manager
(2) Click Add, from here you will find the location where you saved the lightfolio.lrplugin (remember this is an unzipped file)
(3) Select that folder. You will then see the Lightfolio plugin with a Green dot beside it. Click Done
(4) Go the left-side menu of Lightroom and you will see the Lightfolio Publisher. Double-click to get it synced with your account
(5) Add your Lightfolio email and password, and then Press Sync Now!
*You will see previous galleries synced to the account, however, you will not see the images from those galleries. Only images that have been published through Lightroom will be seen. So, let's published some photos to Lightfolio*
(6) Create a new gallery in Lightfolio and then resync your account in Lightroom. You will see this new gallery appear.
(7) Click on the drop-down arrow next to the gallery and you will see a sub-folder entitled Images.
(8) Select the images in Lightroom you want to publish to your gallery and drop them into this Images folder
(9) Right click on the Images folder and then select Publish Now
If you then return to your gallery in Lightfolio, you will see the images slowly being published. Feel free to refresh the page to the view the status of the upload.