If you click on "Create or view your tree", your tree will open in a new window, so you must make sure you allow pop-ups. If this doesn't work, try pressing control + F5 on your keyboard. This will clear your cache and refresh the page.
The first view you see will be of the tree builder immediate family page. This is where you can add names. At the top of the page you will see other views - "full family", "Ancestors" and "Descendants". Select the view you wish to see.
To search for a relation in your tree, enter the name of the relation in the search box on the top right-hand side and click the search button. In the search results click on the name and you will be taken to their place in your tree. The search tool is very useful when you have built a very detailed family tree.