The help center is offline from a couple of months now, see this blog post and as @tomscharbach said, it's being rewritten (Good news!).
man pages is your friend.(the manual for a given command)
For example to see the manual for the package manager that Solus uses you can open a terminal and type man eopkg
or eopkg --help
and it brings everything you can do with it. Works with almost every command in linux. (don't be afraid of using the terminal just don't mess with the system unless you know what you are doing)
And welcome to solus!