Motion capture and 3D model formats
You are a little confused in the MoCap process.

Most mocap is captured live on either a soundstage or direct to your computer with a webcam/video camera with specialized software. This software converts the action footage with markers into data (usually xyz coordinates for each marker on the model for the time of the motion. This data is then used to move the 3D model with the motion file (there are several file formats, 'bvh' being the most generic).

You can also purchase motion data of a variety of actions from certain companies that sell their data online. The motion data will only work with models that have a 'skeleton' file embedded with the object file. There are several file formats that ave used for this. Models by 3D Studio, Maya, Poser, Daz Studio have their models available with the 'skeleton' file available.

Learning this on your own will be quite a challenge! I used to teach whole classes in college dedicated to these individual parts of 3D computer graphics!

I would recommend going to the Daz Studio site, or the Poser site for a ton of information about this subject. Have fun!