How to change a site's permissions in Chrome
There are basically two ways to manage the permissions for microphone and webcam to a site: from the Omnibox or inside Chrome's settings.
Change a site's permissions from address bar
This method works when you've already set the permissions for the microphone or camera and want to change them while visiting a particular site.
Go to the website for which you want to change the permissions and click the lock icon on the leftmost side of the address bar:

From the menu that appears, click either the microphone or camera, then from the drop-down menu, select “Allow” or “Block,” then click the X to save your changes:

After saving your decision, you will have to reload the page for the changes to take effect:

How to view permissions from chrome settings
Click to copy these links and then paste in your web address (URL) area:
- Site settings:
chrome://settings/content
- Mic:
chrome://settings/content/microphone
- Cam:
chrome://settings/content/camera
Within Chrome's settings you can manage the default mic and camera, while also allowing or blocking specific websites access to your microphone or camera.

If you're still having problems setting permissions, you can also try to read the official support article for Chrome.
Operating system settings
Windows
In Windows 10, you can set a default Mic, but there are also system-level permissions to allow applications to access your microphone and camera. For both, open up your system settings by clicking on the Start menu and selecting the Settings gear.
From the Windows Settings page, choose System. Within System You can click on Sound or Search for Microphone or Camera. Within these settings you can adjust both the default devices and privacy settings. Type in the search area or click Sound, Microphone, or Camera.
Microphone settings and permissions
You can adjust your microphone settings within Sound

You can adjust privacy settings within microphone privacy settings

Camera settings and permissions
Similar to microphone settings, you can search Cam or Camera, then choose Camera or Camera privacy settings. Unlike the microphone settings, there isn't a specific area to choose a or change your default camera.

If you're still having problems setting permissions, you can also try to read the official Windows support guide.