Redmine

Hi, I have the Redmine 3.4.4 version installed, ruby 2.5.1-p75 (2018-03-29) [x86_64-linux-gnu] and it is mounted on Ubuntu Server 18.4, the problem I have is that at the time of adding a plugin it does not execute them and in most of the locations they tell me about a vendor / plugin folder. in which I can't find her.
where the Mega Calendar plugin is migrated is in the following location / usr / share / redmine / public / plugin_assets
Is it the correct location or do I have to add it elsewhere.

Thank you for your attention and I await your comments.