Page Header Text

If you have the Typography add-on, you can do it easily in the Customizer.

If not, you can use CSS:

.main-title {
      font-weight: bold;
      font-size: 30px;
}

I mean the page header - if i go to pages and scroll down it says page header with two options image and content. I want the text in the content section to be bigger and bold

Ah, well you can do something like this then:

<div class="large-text">
      My large text in here
</div>

Then add this CSS:

.large-text {
      font-size: 30px;
      font-weight: bold;
}