This demonstrates how to login to the Reddit API via OAuth. This assumes you already have an access token and refresh token. If not, you can checkout this video or consult Reddit's docs for assistance.
In the NuGet Package Manager console:
Install-Package Reddit
using Reddit;
...
var reddit = new RedditClient("YourRedditAppID", "YourBotUserRefreshToken");
Console.WriteLine("Username: " + reddit.Account.Me.Name);
Console.WriteLine("Cake Day: " + reddit.Account.Me.Created.ToString("D"));