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Deploying and administering a website/service covers multiple fields separate to programming - you're going to want to primarily look into DevOps, SysAdmin, and infrastructure. Like programming, there are a lot of areas to specialise in as well that depend on what stack you need.
Considering your inexperience in the field, a Platform-as-a-Service product like Heroku might be a good place to start. If you need something more serious with more configuration, an Infrastructure-as-a-Service product like AWS may be better (plus they have many hosted Software-as-a-Service products for things like authentication). If you want to roll your own servers you'll want to look into Docker, which makes it simple to deploy isolated versions of your project (+ any databases) on any machine.
All these products are well documented with guides aimed at beginners - the trick is knowing where to look ;) If you give me some specifics about your project I can probably point you at some basic guides for AWS.
I should also give you the warning that all of these options carry some security risks if you're careless - they can be all configured wrong or exploited through vulnerabilities in your code, which can result in a large bill or (if you're running on your own infrastructure at home) put your personal data at risk.
You'll definitely want to study DevOps and SysAdmin if you're looking for general knowledge. O'Reilly textbooks are a good place to start.
If you're website is entirely static, you can actually host it for free with Github Pages. For deploying a .NET (or really any dynamic) app you probably want to look into how to package it into a Dockerfile. That makes it platform agnostic and bundles every dependency into an easy to deploy image. After that you probably want to look into setting up Heroku to put your app on the internet. You'll also want to maybe register a domain and configure DNS if you want a proper domain name, but that's comparatively simple.
If you're going the AWS route, you'll want App Runner or EC2 for the app itself, RDS for database, and maybe even API Gateway to sit in front of your service and route requests/terminate authentication. You could even configure everything with code using an Infrastructure-as-Code tool like Terraform.
If you can't tell from the number of links, the barrier of entry to AWS is much higher but it's worth getting your head around depending on where you want to go. Maybe leave it until you're a bit more comfortable with building an deploying apps though, I'm mainly mentioning AWS to give you an idea of what you might want to head towards, you should probably stick with Heroku for now.