how to align the text of my posts to the left

Hey, vista.econ!

If you don’t have a child theme, you can install a plugin called “Simple Custom CSS” and it should work. In either case, enter the following CSS code:

.sidebar .entry-header, .sidebar .entry-content, .sidebar .entry-summary, .sidebar .entry-meta {
max-width: 100% !important;
padding: 0px 376px 0px 60px !important;
}

You can adjust the 60px on the line that begins with “padding” to your taste.

I mean align the text inside each post (not the whole design of the site).

Hmmm. I’m looking at it and it already looks aligned to the left.

It is on the mobile site, not via desktop.

Well, it is left aligned with Windows Explorer, not with Firefox. I guess this might be a Firefox problem, not WP related.

It is one of those browser related issues, such as the reduced screen display on Chrome.