You can open a Gantt Chart view, add the 'Unique Reference Number' and 'Dependencies' columns. The unique ref. number is a unique id which belongs to a unique task, the dependencies column will contain the unique ref number of the task you want to create a link with.
% are what we call 'unit', in your case, it means that you guy is planned to work 200% of his time. Check his allocation by going to view, resources sheet and search for the red allocations, and reduce them !!