Maggie - to find the microphone, from the W10 start panel, click on the "Settings" icon (the little cogwheel symbol down the extreme left hand side, immediately above the Power on/off icon.

The settings screen will open with a search bar at the top. Type "microphone" into the search bar and hit return. You will be offered a list of options.
Click on "Set up a microphone" and you will be taken to a page headed "Speech".
Scroll your way down the choices there - choose your language, choose the default voice for apps (I liked George but slowed down just a little!), and eventually you get to Set up a Microphone.
Just follow the instructions. The system asks you to read a sentence aloud from the screen to ensure it can hear you clearly. Keep working your way through the screens until you're done.

And the best of luck!

Thank you very much for your help Andere.It is still not working for me.It is a windows 10 problem with the built in microphone.Don't know what the next step is as yet.

You could try typing Win 10 + microphone + problems into a search engine and see what comes up. There are loads of forums out there where these things get discussed and you can find a fix. Failing that, join one of those forums yourself and ask the question. Chances are that someone knows the answer.
It also occurs to me that your problem might be due to one of your registry files becoming corrupted. If you have System Mechanic or CCleaner installed, you could try running a registry scan and see if it will fix it.