Unfortunately, there is not a way to remove the header bar unless you are in an app which is full-screen and chooses to hide that information. However, you can crop the image in the Photos app:

1. Take Screenshot
2. Open Photos app
3. Open screenshot
4. Press Edit in upper-right of screen
5. Depending on rotation of screen, look for the Crop symbol
6. Press Crop and drag the white boxed frame to match the image you'd like
7. Press Done to finish cropping

Here is a Wikihow on how to do it, with screenshots.

Unfortunately, there is not a way to remove the status bar unless you are in an app which is full-screen and chooses to hide that information. However, you can crop the image in the Photos app:

1. Take Screenshot
2. Open Photos app
3. Open screenshot
4. Press Edit in upper-right of screen
5. Depending on rotation of screen, look for the Crop symbol
6. Press Crop and drag the white boxed frame to match the image you'd like
7. Press Done to finish cropping

Here is a Wikihow on how to do it, with screenshots.