How to center a title in the header using class attributes?

Question

I started to study Bootstrap now and I’m having trouble understanding and modifying the codes in CSS of the folder I downloaded on their website, so it would be easier to edit on the HTML

I need to center the text REGISTER, but I’m not getting it at all and in the files of CSS, several quotations are made about the class and it seems that it is overwritten several times, so if I mess with one, I need to change the others as well.

<header class="masthead clearfix navbar navbar-dark bg-dark">
    <div class="logo">
        <img src="images/drawing2.png" width="9%"/>
    </div>

    <div class="inner">
        <div class="nav justify-content-center m-auto">
            <h3 class="masthead-brand"> CADASTRE-SE </h3>
        </div>
    </div>
</header>

Answer 1

You can center text using the class text-center just inform her in the attribute class tag H3 and in the attribute class tag img inform img-fluid and take out the attribute width, also create the Stylesheet:

<style>
img {
    max-width: 100%; /* largura máxima de 100% */
}
</style>

img {
  max-width: 100%;
}

<link href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta.2/css/bootstrap.min.css" rel="stylesheet">
<header class="masthead clearfix navbar navbar-dark bg-dark">
    <div class="col-xs-12 col-md-2 logo">
        <img src="https://upload.wikimedia.org/wikipedia/commons/a/ab/Logo_TV_2015.png" class="img-fluid" />
    </div>

    <div class="col-xs-12 col-md-8 inner">
        <div class="nav justify-content-center m-auto">
            <h3 class="masthead-brand text-center"> CADASTRE-SE </h3>
        </div>
    </div>
</header>

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References

• Responsive images
• Text Alignment