Double click on the text thumbnail in the layers panel (looks like a capital T) That will highlight the entire text. In the top tool bar you can now set the font size.
When you place an image it has anchors around it Click on one of the corner and drag outward, that will scale it up. Generally what happens is the resolution of the image is less than that of the document you are working on. If that is the case, be prepared for the quality to degrade as you scale up, it will essentially become blurry. Therefore it is up to you to decide how much of a quality loss you want vs the size of the image. When your happen hit the return key or the check mark in the top tool bar to commit.