The video you tried is the best tutorial I’ve ever seen. I don’t know why it did not work for you. But anyway, if you have network connection during the installation, you can use a URL as @jlehtone suggested. For example,
inst.dd=https://elrepo.org/linux/dud/el8/x86_64/dd-megaraid_sas-07.719.03.00-2.el8_7.elrepo.iso
This is assuming you are installing EL 8.7 and your driver is megaraid_sas.