Add ACfL system package steps for RHEL 9

Author: LukeIreland1

content/install-guides/acfl.md

@@ -197,6 +197,31 @@ sudo yum install acfl
 
 The ACfL tools are now ready to use.
 
+### Red Hat Enterprise Linux (RHEL) 9 
+
+Arm Compiler for Linux is available to install with either the `dnf` or `yum` system package manager.
+
+#### Install ACfL from the RHEL 9 package repository
+
+Install ACfL and prerequisites from the RHEL 9 `rpm` package repository with `dnf`:
+
+```bash
+sudo dnf update
+sudo dnf install 'dnf-command(config-manager)' procps psmisc make environment-modules
+sudo dnf config-manager --add-repo https://developer.arm.com/packages/ACfL%3ARHEL-9/standard/ACfL%3ARHEL-9.repo
+sudo dnf install acfl
+```
+
+Or using the equivalent `yum` commands:
+
+```bash
+sudo yum update
+sudo yum install 'dnf-command(config-manager)' procps psmisc make environment-modules
+sudo yum config-manager --add-repo https://developer.arm.com/packages/ACfL%3ARHEL-9/standard/ACfL%3ARHEL-9.repo
+sudo yum install acfl
+```
+
+The ACfL tools are now ready to use.
 
 ### Set up environment