Something is wrong with tags

This is Roberto, a BeTheme user. I am going
crazy with some stuff about tags and was wondering if you could give me a hand.
Two main problems I cannot solve by myself:

1)     
CLASSIFYING
POSTS IN A PAGE BY TAG. I want to classify some pages with posts by tags. I
mean, let´s say for example the page "Dog Documentation", ok? In that particular
page I just want to show the posts with the tag “documentation”. But I just can
see the option in the editor of classifying by category. Do you know how I can
do this?

2)     
TAG
CLOUDS. When I click one tag in the tag cloud widget you don’t go exactly to a
page with the posts with that tag, but with all the posts. Do you have an idea
what is going wrong?

Maybe I need to install a specific plugin?

Thanks,

Roberto