Hi there and welcome Mary
Can you please hold the home and power buttons for about 10 seconds on the iPhone until you see the Apple Logo, then release.
Let the phone restart and tell me please if the touchscreen is now working.
Did the apple logo come up Mary?
And did it then restart?
You will have to reset the iPhone, This will remove all data but you cannot avoid this
To do the reset
Connect the phone to the computer and open itunes
Hold the power and home button down until you see
"iTunes has detected an iPhone in recovery mode..."
Click Restore Phone, let this complete and it should now work
Let me know the results please