Can you please help me create the 3 main reasons for this thesis?Thesis: social networking sites / technology do enhance relationships.

The 3 "main reasons" you seek are actually the
sub-categories for your argument.  You are proving that social networking sites and
technology do enhance relationships.  Brainstorm.  How?  How do
social networking sites and technology enhance relationships?  Make a long list.  Write
answers that are both general and specific.  Include personal examples, observations,
and things which you have heard on the news or read
about.

Once you have a long list of ideas (more than 10
would be best), you can look at your ideas and see what categories they seem to fit
into.  Off the top of my head, I'm guessing one main category is going to have to do
with the fact that social networking and technology have made keeping contact and
building relationships more
convenient.

Your other sub-topics are going to
depend entirely on the list of examples you personally can brainstorm.  If you need more
help in the brainstorming stage, I encourage you to post a question in the discussion
forum and combine answers from several different people.