pagedown HTML resume - how to increase font size and reduce margins

Question

I am using the pagedown template resume, which is accessible by starting a new R markdown file and choosing "From Template" and "HTML Resume".

I have pasted the YAML header below.

---
title: "Lijia Yu's resume"
author: Lijia Yu
date: "`r Sys.Date()`"
output:
  pagedown::html_resume:
    # set it to true for a self-contained HTML page but it'll take longer to render
    self_contained: false
# uncomment this line to produce HTML and PDF in RStudio:
#knit: pagedown::chrome_print
---

The normal adding of fontsize: 12pt or geometry: margin=1cm doesn't work for me.

I did try adding some CSS (which I don't know too well), but it overrides the template and I want the formatting of the template to stay intact, just larger font and reduced margins.

I also found this snippet that removes the sidebar on the 2nd page. I'd love to incorporate this code as well:

```{css, echo=FALSE}
.pagedjs_page:not(:first-of-type) {
  --sidebar-width: 0rem;
  --sidebar-background-color: #ffffff;
  --main-width: calc(var(--content-width) - var(--sidebar-width));
  --decorator-horizontal-margin: 0.2in;
}
```

How to keep the general formatting of the HTML resume with larger font, smaller margins, and incorporate the code to remove the sidebar on the 2nd page?