Text not in the center of the webpage

I have a div named calculator-frame that contains a frame for a calculator website I’m making in a webpage, I’m using CSS Right now, I already have everything in the html file.

The problem is that I can’t make the text align in the center of the page, also, the buttons of the calculator are not in the center same as the title text. (not the document title)

This is the code I tried to align the text to the center of the webpage.

#calcTitle {

    font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif ;
    position: relative;
    color: darkblue;
    align-content: center;
    padding: 10px;
    float: left;
}

I used Align-content to make the title in the center of the webpage, I used that same keyword for the buttons.
The result is that the Title in the screen is not in the center of the webpage.

I appreciate any tip/help,