You did not read the FAQ
here
http://manual.calibre-ebook.com/faq.html#id10 or you would know most of the answers.
2(maybe 3) simple choices depending on connectivity and system availability.
1)Calibre content server running on a 24/7 system (this content is read only to clients). Clients use a standard Web browser to dowload content for viewing with user supplied
viewers (like Acroreader)
2) Sneaker-Net. Copy the
Calibre Library folder to each PC capable of running Calibre, Just point the Local Calibre to that folder.
Do Not combine Libraries (just copy onto an existing Library), Only delete and replace the entire folder contents if it is the same library being
refreshed or you will gain lots of cruft.
3)Put your library in Drop box, only 1 system can be connected at a single time to avoid damage.