Installation via Web UI - w2c/letsencrypt-esxi GitHub Wiki
1. Storage -> Datastores
Use the Datastore browser to upload the VIB file to a datastore path of your choice.
2. Manage -> Security & users
Set the acceptance level of your host to Community.
3. Manage -> Packages
Switch to the list of installed packages, click on Install update and enter the absolute path on the datastore where your just uploaded VIB file resides.