I'm having a lot of trouble finding documentation for Sitecore 9 and setting everything up. I installed Sitecore 9 and have a working website, but how would I add another website instance? In 8, it was as easy as using the SIM so I'm just confused how to do so with 9.
There are several ways to install multiple versions of Sitecore side by side locally.
1. "Sitecore Install Assistant":
"Sitecore Install Assistant" is a graphical user interface that Sitecore provides with Sitecore 9.2 and 9.3. You can download the package on the same page where you download the packages for Sitecore 9.2/9.3. It allows you to install the Sitecore prerequisites and if you want it installs a secured Solr instance. You may install as many instances as you want. Make sure to use different Solr Instance name Sitecore Instance name for each new instance.
Download "Sitecore Install Assistant" 9.3 package:
Sitecore Install Assistant
Tutorial on how to use it:
Sitecore v9.3 Installation with "Sitecore Install Assistance"
2. Install Manually with SIF:
You may install it manually with SIF. First I would recommend you to understand the SIF scripts, that is the most important step. Secondly, make sure to read the Sitecore installation document. The next step is to install all the prerequisites. Once you completed these steps you can start to install a second instance. Make sure to create a separate Solr instance and different versions of Sitecore may require different versions of Solr. Update the SIF (XP0-SingleDeveloper.ps1) and use the new Solr name and use a different Sitecore instance name. There may be other parameters that you have to change so the installation does not override your previous installation.
3. Use "Docker Containers":
If you never used Docker this approach will be the hardest. However, if you want to learn to go for it. First, install Docker locally and get familiar with Docker. Understand what Docker images and containers are and how to create an image and run a container. The second step is to install Sitecore Docker images and the third step is to run a Sitecore Instance in a Docker container. Below I will provide really good resources where you can learn Docker for Sitecore.
From Dylan Young:
Introduction to using Sitecore Docker Images
From Viet Hoang:
Playing around with the set-up of Sitecore Docker Images
4. Use "Sitecore Instance Manager (SIM) 1.6":
Sitecore Instance Manager (SIM) 1.6 was released yesterday and it supports Sitecore 9.0- 9.3. SIM is a very easy and handy tool to install a Sitecore instance locally.
Sitecore Instance Manager 1.6