Add Cardinal and TMAP8 to installation instructions

Refs idaholab#38 and idaholab#52

doc/content/getting_started/installation.md

@@ -59,20 +59,43 @@ To compile FENIX, first make sure that the conda MOOSE environment is activated
 conda activate moose
 ```
 
-Then navigate to the FENIX clone directory and download the MOOSE submodule:
+Then navigate to the FENIX clone directory and download the MOOSE and TMAP8 submodules:
 
 ```bash
 cd ~/projects/FENIX
 git submodule update --init moose
+git submodule update --init tmap8
 ```
 
-!alert note
-The copy of MOOSE provided with FENIX has been fully tested against the current
+Finally, Cardinal and its dependencies must be downloaded and pre-built. To perform this, first run
+the build script from the FENIX clone directory:
+
+```bash
+scripts/update_and_rebuild_cardinal.sh
+```
+
+Then, to download OpenMC cross sections needed for OpenMC-based Cardinal runs, run:
+
+```bash
+cd ~/projects/FENIX/cardinal
+scripts/download-openmc-cross-sections.sh
+```
+
+and subsequently set the location of those cross sections in your environment:
+
+```bash
+export OPENMC_CROSS_SECTIONS=~/projects/FENIX/cross_sections/cross_sections.xml
+```
+
+!alert! note
+The copies of MOOSE, TMAP8, and Cardinal provided with FENIX have been fully tested against the current
 FENIX version, and is guaranteed to work with all current FENIX tests.
+!alert-end!
 
 Once all dependencies have been downloaded, FENIX can be compiled and tested:
 
 ```bash
+cd ~/projects/FENIX
 make -j8
 ./run_tests -j8
 ```
@@ -88,10 +111,10 @@ FENIX is ready to be used and further developed.
 
 ## Update FENIX
 
-FENIX (and the underlying MOOSE Framework) is under heavy development and is updated on a continuous
-basis. Therefore, it is important that the local copy of FENIX be periodically updated to obtain new
-capabilities, improvements, and bugfixes. Weekly updates are recommended as, at minimum, the MOOSE
-submodule within FENIX is updated up to several times a week.
+FENIX (and its underlying dependencies MOOSE, TMAP8, and Cardinal) is under heavy development and is
+updated on a continuous basis. Therefore, it is important that the local copy of FENIX be periodically
+updated to obtain new capabilities, improvements, and bugfixes. Weekly updates are recommended as,
+at minimum, the MOOSE submodule within FENIX is updated up to several times a week.
 
 !alert note title=Always update FENIX and the Conda packages together.
 There is a tight dependency between the libraries and applications provided by Conda, and the submodules that FENIX depends on. Therefore, when you update one, you should always update the other.