There is a sample in the readme of this repository:
public async Task<IActionResult> Callback(string code)
{
// Validate the code we just received
// The response data should be stored somehow (authentication cookie / .net core identity)
// https://docs.microsoft.com/en-us/aspnet/core/security/authentication/cookie?tabs=aspnetcore2x
SsoResponse authentication = await _sso.AuthenticateAsync(code);
// Information in SsoResponse includes a refresh token if any scope was requested
// To refresh information, just pass the refresh token to the RefreshAsync method
// Example: SsoResponse refresh = await _sso.RefreshAsync(authentication.RefreshToken);
// Use the access token to get information about the character that logged in
SsoCharacter character = await _sso.VerifyAsync(authentication.AccessToken);
// OPTIONAL: Redirect to a specific location as specified in Login step
return RedirectToAction("Index", "Home");
}