How to combine different projects to create final clip in after effect?

Hello;

i am newbie and learning adobe after effects cs6. I have downloaded  different templates from web and edited them according my wish and now i  want to create final movie by combining all the clips.

Some clips/projects are with different resolution, i have rendered all projects separately and created individual .mov clips.

Now i want to create final movie by combining all the clips.

As  i stated above i am completely newbie so please guide me with details, hope you guys wont mind it.

Iam working with adobe after effects cs6.

Thanks