Noone can see the whole global tree, because after 10+ years it is very very big. Millions of connections.
In answer to your questions, yes you will need to add your ancestors and continues adding them, along with sources as far back as you can do.
You should add in siblings, their spouses, nieces, nephews, grandchildren and so on, along with sources, to each new generation you add.
You do this because it increases the chance of making a connection. The more relatives you can add, the sooner you may find someone who is already on the global tree.
For some people it may take a while to make a connection. But please do not get discouraged.