You can change the size of your text for the entire project at once, or on each individual block.
Text Size Throughout the Entire Project
You can change the size of the text for the entire project under the Design Settings tab at the top of the Workspace. Click on size, and use the slider that appears to adjust the size of your text.
Text Size on Individual Blocks
Open the block with text you want to change. Click on the text field that you want to edit to bring up the edit menu. Select size from the menu, and use the slider to adjust to the size that you want.