Indenting paragraphs only in blog post

I entered the following code in the “Edit CSS” link under “Appearance.”

p {
text-indent: 1.5em;
}

It’s the only code I had (I removed it since) in that section. No other CSS manipulation done under “Edit CSS.”

While it did create indents in the paragraphs of each blog post, it also indented other things which I did not want to be indented. For example, in the sidebar,

“Subscribe to Blog via E-Mail

Enter your email address to subscribe to this blog and receive notifications of new posts by e-mail.”

The word “Enter” was indented.

I get the concept of CSS, but I guess I’m struggling to find out which particular element I can enter this code for in order to only get indentations for paragraphs in a blog post and also the static front page. Nothing else.

Here is my blog:
https://ateret-tiferet.com

I am using Quintus theme from https://www.wordpress.com which I have modified for my own use (manipulating the CSS code). However, it is not heavily modified. Basically, coding for Palatino Linotype font, no underline for hovered links, etc. Small things.