Changing H1 tags for SEO

RE: slider by 10web

I have the slider above on my home page. I ran an SEO plugin and it says the slider is using H1 tags for the text on each slide and there are 4 slides. They recommend I convert these tags to H2 so only the page title uses an H1 tag as multiple H1 tags on the same page hurts my search engine performance. What I don’t know is how to do this. If you could assume any instruction you’d be giving would be to the equivalent of a 5 year old that would be appreciated.