How can I adjust the margin in my website's textboxes?

[Rasmine]

Hello.

I have a problem with my textboxes on my website. I want to push the textbox more in the middle of the page.

But the adjust features does not allow me to move the textbox. How can i add more distance from the left margin and my textbox?? ://

[Guleria]

Can you share the store URL ?
 And highlight where you need a gap much better if you share a screenshot.    

[Rasmine]

URL:  https://www.underflod.shop/pages/firmagaver

[Guleria]

Follow these steps:

1. Go to Online Store -> Theme -> Edit code

2. Open your theme.css file and paste the following code at the bottom:

section#shopify-section-template--20793497583951__rich_text_Dde34k {
    margin-left: 10%;
    margin-right: 10%;
    border: solid;
}

[Rasmine]

But if it is not for the whole theme, but only for one unique textbox?