I would like to play some live games against the computer but I don't find it.

Somebody can help me?

See the green menu bar above?

Play/Live Chess.

Then click on Live Chess.

You should see a graph on the right, with dots on it.

The light green ones are computers. Move your mouse cursor over them to see their rating/difficulty etc.

Click on them to play.

Thanks, I know what happened. In my settings showing computer players was disabled.