Problems trying to integrate Facebook Page

Hi, I´m using OJS and I´m trying to show a Facebook Page in the sidebar.
I´ve tried two methods without succes:
First, by using Custom Block. I´ve add the code in a source field, but I don´t know where to put the head script ¿There is a plugin to integrate scripts in the head tag?

Second, by installing Custom Header. Here I’ve another problem. I can´t install plugins from the Plugin Gallery, because when i click in the install button nothing happens. In other topic I read that it could be my PHP version. I downgraded the php, but the site stoped to work, so I´m using Php 7.0 again. Later, I´ve tried to install the plugin manually in the folder plugins/generic (I´ve done this before with other plugin), but when I go to the Plugins manager It doesn´t load anything. So, I delete the plugin and everything works but I´m stuck. I can´t integrate Facebook. Please help