You can modify the title of your portfolio and change other design aspects of it via the WordPress Customizer. This interface allows you to see a preview of your portfolio as you change settings.
Access it via the Customize link at the top of your black WordPress admin bar while viewing your site or from inside your dashboard via Appearance -> Customize.
Each panel on the left side provides tools to change the appearance of your site. Let’s start with the first one, Site Identity.

Change the site title and the tagline in the Customizer.
As you change the text in the left side editing fields, you will see the changes previewed on the right. We might start by creating a more personal title.

Start by changing the title of the portfolio site.
No changes are made to your site until you click the Publish button at the top, so we can do a few more things.
Let’s change the image shown at the top of the site. Open the Customizer panel for Header Image.

Click ‘Add Image’ to upload your own photo to use in the header of your site.
Now this site is looking different than the default template!

Your own image will now be on every page of your portfolio.
Perhaps the new background image does not look good with the white of the text title. Open the Colours panel of the Customizer, and use the left side selected to choose a new colour for the Header Text Colour. As you change the selector, you will see the changes on the right side.
You can also choose to have a different background color for the text page; make sure you use one that has sufficient contrast with the black text.

Choosing new colors for the Header Text and the page background.
The Customizer for this theme provides a set of tools to modify the appearance of the Hearts theme’s front page display of most recent portfolio artifacts. These tools are in the TWU Portfolios panel of the Customizer.

In this panel, you can change the text of the title and subtitle (“tagline”) that appear above the display of your most recent artifacts. Use the drop down menu to select how many artifacts it should show on the front page.
Now explore other things you can change here. If all these changes look good to you, click the Publish button to make them active.
