To replace the home page slideshow with an image first you to create a static block and add your image as content to that article. Then you need to edit the home page header and set its Primary content option to reference your new static block instead of a slideshow.
With regard to your question about the BuddyPress plugin, we can’t help with that. If you need help installing, setting up and using the BuddyPress and bbPress plugins please ask in their dedicated support forums…
BuddyPress support → https://buddypress.org/support/
bbPress support → https://bbpress.org/forums/
If you are struggling to get to grips with the Salutation theme we have some videos and tutorials that may help…
Razor videos → http://para.llel.us/support/videos/
Razor tutorials → http://para.llel.us/support/category/wordpress/razor/
If you need to learn how to use WordPress then I can recommend the WordPress Lessons, they are a fantastic resource…
WordPress Lessons → http://codex.wordpress.org/WordPress_Lessons
If you can’t get on with the lessons and you need more help then you can ask questions in the appropriate WordPress support forum…
WordPress Support → http://wordpress.org/support/
If there is anything else about the Razxor theme itself you need help with, please just let us know. If you can’t find a solution using the forum search please create a new topic for each separate issue and we’ll do our best to help.