Once you have your API key, just add it to the Api Keys in the Settings section (Under General Tab), making sure your key name is TinyMCE. Like shown below
TinyMCE Api Key added
Settings
You can optionally choose which menu items and tool bars to show to the editor on the property settings when you have added it to the content type
Example of getting value on page
We have to use the (MarkupString) on HTML content in Blazor