It says in the readme for All Natural that I need to "rebuild my bashed patch" by "selecting "Import Cells" from "All Natural.esp" and "All Natrual - SI.esp". Trouble is I don't know where the Import Cells button is and I also don't know which tool to use. Can anyone help me? I've looked through Wrye Bash and OBMM and can't find anything.

Read the section on the Bashed Patch in the Wrye Bash readme. Also, next time you have such a specific question, it would be a good idea to post in in an appropriate thread, rather than make your own. In this case, the thread would be the official Wrye Bash thread, since that's what you're having trouble with.