BresponZive

Hello guys!
I install free theme – BresponZive , and when i put some images in post for Slideshow, or for post, images are not showing good, i mean all images are so large for it.. how can i know what pixels i need to upload for posts and slideshow`s?
And i cant understand how to configs menus for this theme? I need put some my menus, but cant find from where?
Sorry for my bad English!
Thanks in advance!