How to replace images from each part?
How to add autoresponder code with news shelter?
This pretty much depends on the section you are editing. For eample, to change images on the main slider, you will need to edit The Slider Revolution:
Other images can be easily replaced using Live editor: http://jmp.sh/0kfMuCg
in some cases the image is used as a row or cell backgrounds: http://jmp.sh/ipQYmSv
There is no autoresponder functionality built into the theme itself, but there are many plugins or third party services (like mailchimp,...) which offer autoresponder functionality. For very simple autoresponders you can even use included Contact Form 7 plugin: https://contactform7.com/faq/can-i-implement-autoresponder/, but it might not be enough, depending on what you want to achieve.