The MIAB installation is really quite straightforward and well documented. Once you have selected where you are going to set your box up (I personally use Digital Ocean, but others use Linode with great success, and @alento has some recommendations as well) you just have to walk through the setup guide: https://mailinabox.email/guide.html
One thing that I will note is that the setup script has EVERYTHING you need, so don’t get a resource with any preinstalled apps or whatever (Including a LAMP/LEMP stack…the set up script will handle all that). Just provision your VPS, set up your login credentials as noted in the setup guide and run the script.
If something goes wrong after that, post questions here and people will be happy to help.