yEd has no support to import .csv format. However, it has support for TGF, a very simple text-based format that lends itself well to import node connection data. (TGF stands for Trivial Graph Format.)
Alternatively, you could also use yEd's Excel import support, i.e. use an .xls file that contains your node connection data. Please refer to the yEd Manual for details. (And using the forum's search feature, you will find additional information relating to the Excel import. The search term 'excel' should be a good start.)