Go to the back end of your site (administration site).

Select Content.

Choose from All Content Items or Static Content Manager depending on whether the content item is a Static Content Item or a Content Item. Click on the relevant one.

From the list in the Static Content Manager or All Content Items click on the item you wish to edit or add to.

Make changes to title,  text or images as desired.

Click the save button.

Go to the front end of your site and refresh your screen to see your changes.

Next, learn more about inserting an image into a content item.