Screenshots are incredibly useful. you can use them to show someone how to use an app, send a strange error message to your IT department, capture tweets or anything that you think is useful. If you’re using an iPhone, this is quite a simple operation.

Press the Side button & Volume up button at the same time. (If using a model with a Home button, Press the Side & Home button at the same time instead).
Your phone will flash (confirming that you have successfully taken a screenshot) and a Thumbnail image of the screenshot will show in the lower left corner.
Tap on the thumbnail image to make it larger.
you will be shown options to let you share or delete in the upper right corner.
There are editing tools available so that you can add highlights or mark it up as needed.
Clicking on the Plus icon (located in the lower right corner) lets you add text, signature, arrows & shapes.
once you are finished, tap on Done in the upper left hand corner.
You can save the screenshot into Photos, files or if you want Delete it.