To edit existing text, first you will want to locate the text box in which you would like to edit. Double click on the text you decided on.
After double clicking the text box, you will see the text box toolbar pop up. This is where you can edit the design of your text.
Within the text box toolbar you will see different design options. On the left hand side you can adjust the styling of your text, whether it be bold, italicized, or underlined. Also you can choose whether you want your text to be left, center, right, or justified aligned.
To the right you have the option to hyperlink text (See Linking Text), control indentations, add numbered and bulleted lists, add an icon, add an image, and un-format your text.
Above the previous list of options you have another row of text designs. First you have the text style (for more info on text styles check the "Design Tab" page section). You can also adjust the color of your text using the option to the far right. Make sure that you DO NOT change the size of the text using the "Size" option, because if done it will undo the formatting of your text.