Now for most of us you really don't want to remove it as much as you want to hide it and I'll show you two ways to remove it:
1st Method (Hide It): As you can you can from the image below you can just click on that 3x3 mini speed dial on the top right corner, as shown below.
2nd Method: (Disable It)
- Open Firefox and type in about:config into the URL bar up at the top and hit enter/return
- Check the box I'll be careful, I promise
- Search for: browser.newtab.url
- Double click it to bring up a small windows with a text box that should say about:newtab
- Change to: about:blank