IF you are migrating to a new server OR upgrading "in place", just change the designated port when asked by the installer.
IF you have already installed ALM, you can "reconfigure" it with the Configuration Wizard.
See this post on Orasi's forum EyeOnTesting about how to run the Configuration Wizard:
The easiest way to change the port (after install) would be to run the "Configuration Wizard" again (it was originally part of the installer), but specify for it to use an EXISTING qcsiteadmin (NOT upgrade NOR create a NEW one). You an tell it to "keep all settings", take the defaults (that are pre-populated), THEN when on the page related to the port, you change it there and continue with the wizard defaults.
[[ you will likely need to provide a DB admin password, and maybe the "td" user password on the qcsiteadmin schema page "schema password" ]]
After it "re-deploys", your QC should be using the NEW port.