Click on the link : default boostrap.
The bootstrap is used to fill the libresource platform with basic content such as help, structure, basic security and so on.
A default one is given by the link provided on the bootstrap page, but for advanced user, you can use your own bootstrap.
In LSC 2.2, the default links tries to get it from
http://localhost:9000/static/download/Boostrap.xml.
If it can not get this file download it from any libresource (same url) and upload it.
Seb