You posted your question in the non-technical Lounge forum, which is where you can connect with your peers for conversations that don't directly relate to product help and support. I'll move it to the Photoshop forum for you.
In the meantime, to answer your question, you can select text with the Type tool and modify text strings using commands from the Options bar, Character and Paragraph panels.
People don't like to click on unknown links, so post images directly here.
Point size is a physical size property. 1 point = 1/72 inch. So the on-screen size depends on the file's resolution (pixels per inch, ppi).