How do I get rid of the RSS feed button in my header?

Also, I’d like to get rid of the “written by [email protected], October 29, 2015, 0 comments” line under headlines

get rid of rss:
add this to your stylesheet
.rss-social {display:none;}

get rid of written by … under the headlines:
.byline {display:none;}

Just be aware that if you edit the theme’s stylesheet directly, you’ll lose those changes if the theme is ever updated in the future, to fix bugs or security issues or to add new features. Better to use a custom CSS plugin or your theme’s built-in custom CSS option, if one exists.

yes use a plugin.

Okay. Thank you very much!