Using Sleep/Wake + Home button
You can capture the screen on your iOS device using the Sleep/Wake and Home button.
1. Press and hold the Sleep/Wake button on the top or side of your device.
2. Immediately press and release the Home button.
To find your screenshot, go to the Photos app > Albums and tap Camera Roll.
Turning "ON" the AssistiveTouch
1. Launch Settings app on your iPhone → Tap on General. Tap on Settings Then General on Your iPhone
2. Now tap on Accessibility.
3. Tap on “AssistiveTouch”.
4. Turn ON “AssistiveTouch”.
Once you follow the above steps, you can see a virtual button in a round shape on your iPhone screen. Tap on the button and you will find options to operate your iPhone without using Home button & sleep/wake (power) button.
Taking a screenshot.
1. Tap on Virtual Button.
2. Tap on Device.
3. Tap on More.
4. Tap on Screenshot.
You now have taken a screenshot on your iPhone.