Here is a list of the basic steps you will need to complete.
- Configure your domain so that it points to your server's IP.
To do this, go to its settings, delete type A records that lead to other addresses (most likely there are one or two, if not, you need to @ A XXX.XXX.XXX.XXX YY out why they are there) and add a type A record to your IP @ A XXX.XXX.XXX.XXX YY , where XXX is the IP of your server, YY is the TTL lifetime.
With the mail here is a separate conversation. If you connect, for example, mail.ru for business, then everything is well written in their documentation.
You can read more about the record types, for example, here or on Wikipedia .
Example: 
- (Optional) If your IP is not static.
In this case, you will often see the phrase "domain delegation". There is nothing wrong with that. It simply sets the storage location for your domain settings. The delegation record looks like this: @ NS xxxxxx , where xxxxxx is the hosting DNS address.
For example, my domain registrar does not have the ability to update the IP domain compliance programmatically, so I use DNS hosting, and the DDNS update script is registered on the router once an hour. So If you change the IP in the worst case, it will be updated in an hour. You can set the refresh interval and another, just this one is more suitable for me.
You can update DDNS even from the server itself, it already depends on the connection method (it is connected directly and has a white IP, or through intermediate equipment and does not have a white address).
- (Optional) Port Forwarding (NAT)
Most likely, your server is behind a router or firewall. Then you will have to create rules for port forwarding to the internal IP of your server.
For example, to open port 80 to your web server, you will have to create a rule like this: Входящий порт: 80, Протокол: TCP, Действие: netmap (название может отличаться в различном софте), На адрес: вашего сервера, На порт: Порт, который прослушивает ваш веб-сервер
Example: 
- Server installation
It is already up to you. What OS you install and what services you deploy on it (web server / server kc 1.6 / or something else)
An example for IIS (the easiest to make it come from): 
In the IIS console, click RMB on the sites and choose to add a website. Choose a name, specify the folder where it is located, write a domain (by which it should be accessed), specify the port. This is enough to run a simple static site. (IIS must be installed. Example below. The easiest way to install the necessary components is to choose Asp.Net. Some other components will be installed along with it. Do not forget to click "Static content" for styles and other static files)

- (Optional) create domains of level 3 of the form lalala.domain.com
A very useful thing for a web server. To create a subdomain, you need to add an A type record to the domain settings. Example: lalala А XXX.XXX.XXX.XXX YY , where XXX is the IP of your server, YY is the TTL lifetime.
Screenshots of settings are given for familiarization and do not pretend to the professionalism of performance!