How to make computer recognise external microphone

Hi Everyone
I am using a small netbook laptop Lenovo about 4 years old. The Windows 10 version is 1903.

Now that we are all locked down I am using zoom a lot BUT so far I have had to use it on my smartphone because on this computer, although I can hear other people, they cannot hear me.I had this problem a few years ago with skype though that seemed to happen after skype upgraded and I blamed skype and the upgrade. Since then for videocalls I have mainly used whatsApp but on phone, of course.

Now that we are all using zoom so much and because I was encountering this same microphone problem - the App apparently not recognising the internal microphone - it was suggested to me that I should buy an external microphone. This I have done BUT it has not helped and the problem seems to be that the computer just does not recognise it is there. If I go to Settings, then System then Sound it is still only giving me the option 'Microphone (Realtek High Definition Audio)' that it always has i.e. the built in microphone.

So my question is: to use Zoom with the laptop, which will be much better for meetings with more than 4 people, how do I connect in the external microphone? (It connects via the audio jack).

Thank you for any help uyou can give.

(1) fix your internal microphone first, have you give the OS and the individual applications permission under settings/privacy to use your microphone.

(2) does your laptop has separate headphone and microphone jacks or is it a single integrated jack?

If it is a single integrated jack for both headphone and microphone, you need a splitter. Or if you have an old android wired headphone/microphone, try to use that for your laptop.