SciLinux is supposed to be in the RedHat/Fedora 'family' (much like CentOS 7 - yum/rpm package managers) so the directions for installing a Moodle found via https://docs.moodle.org/35/en/Installing_Moodle should be close enough ... adjusting for the differences in package manager repos and firewalls.
There's another https://docs.moodle.org/35/en/RedHat_Linux_installation but as you can see specific to RH.
Suggest sharing what problems you've had and they probably can be addressed.
Will ask one question however ... what does:
yum repolist display to you when issued as root user or sudo?
And, for reference:
https://www.scientificlinux.org/documentation/customize-sl-for-your-site/
'spirit of sharing', Ken