You can zoom in and out the graph with the mouse wheel. You can move the graph by clicking and holding the left mouse button and moving the mouse.
When you click on a language node in the graph a modal window with information about the language will be displayed.
Search for a language name from the top menu to highlight its connections. Languages in red influenced the highlighted language and blue ones were influenced by it.
Choose and click on a paradigm from the Language Paradigm menu to only show languages within this paradigm.
You can choose between a Force Atlas 2 and a random layout. When you change the layout all languages will be shown.