Hi @nef,
Here is the link to the latest release: Releases · elifesciences/lens · GitHub
You just need to download and unpack lens-2.0.0.zip and overwrite corresponding files in the plugins directory. From you web root it will be here: plugins/generic/lensGalley/lib/lens
Don’t forget to make a backup just in case. I haven’t got any troubles in upgrading process.