Adding a third dfs member to replication group

I am getting ready to add a third dfs member to my replication group. I am installing DFS services on the Win 2008 R2 Standard server, when it ask me to enter a namespace do I enter my existing namespace or do I select create namespace later?  I do not want to create a new dfs namespace. I would like to use my existing namespace \\mydomain\data and add this server as a member.

Thank you.