Best place to edit Title, H1, and meta tags for SEO?

Using the analysis available at Moz, I’ve determined my site isn’t very search engine friendly. The primary suggestions are to have:

1. Unique Page titles that are SERP friendly
2. Use meta descriptions
3. Use H1 tags

Do I just need to go into the individual page’s code to edit each of these, or is there a better method?

Thanks!