You can use built-in WYSIWYG editor to change the text style:
Or you can change the source code:
This is italic font-style
<p><em>This is italic font-style</em></p>
This is bold font-style
<p><strong>This is bold font-style</strong></p>
This is your underlined text
<p><span>This is your underlined text</span></p>
This text is deleted
<p>This text is <del>deleted</del></p>
This is an important marked text
<p>This is <span class="text-primary">an important marked text</span></p>
This is an important blue text
<p>This is <span class="text-info">an important blue text</span></p>
This is an important yellow text
<p>This is <span class="text-warning">an important yellow text</span></p>
This is an important red text
<p>This is <span class="text-danger">an important red text</span></p>
Gray paragraph style
<p class="fr-text-gray">Gray paragraph style</p>
Bordered paragraph style
<p class="fr-text-bordered">Bordered paragraph style</p>
Spaced paragraph style
<p class="fr-text-spaced">Spaced paragraph style</p>
Uppercased paragraph style
<p class="fr-text-uppercase">Uppercased paragraph style</p>
Left aligned text
<p style="text-align: left;">Left aligned text</p>
Center aligned text
<p style="text-align: center;">Center aligned text</p>
Right aligned text
<p style="text-align: right;">Center aligned text</p>