Adding a Textbox
First, select/make an image to add a blog/textbox to. I'm using this image of Ellen Page:
Select the Rectangle Tool or whatever setting it's on. You can locate it here:
Change your settings to mine:
Now make a new layer and select the color white.
Now drag the cursor to about how to want your textbox to be. Here is how mine looks so far:
How go to your layer palette (if yours isn't visible go to window >> layers) and change the fill opacity to about 60-70:
I also added a stroke to mine:
(drag this one to address bar for fullsize)
Now, add whatever you want, like a shadow and text, and here you go! This is my finished product:
You have now created a textbox in photoshop. Wooo!