Joaquin, since you didn't yet know how to set unix file permissions
with chmod and fire up a text editor of your choice, you'll want to
move learning such things up on your list of priorities.
It might or might not be a good choice for you, and it's certainly out
of date now, but a dozen years or so ago now when I was first learning
Unix, I personally found
UNIX For the Impatient
to be excellent. If you haven't already, I recommend asking around
for good "intro to unix" sorts of books. Plenty of other folks here
could probably give recommendations...
In some very unusual cases (e.g., an OpenACS Bootcamp or training
class) it can be possible to be productive with OpenACS while knowing
nearly nothing at all about using Unix ("Um, 'ls', did that have
something to do with listing files?"). But that's unusual, and
definitely isn't the case for you, because you're installing
OpenACS and dotLRN yourself from scratch, and presumably will be
maintaining it, doing development work, etc.
In general, learning basic unix use will serve you very well
in the future, and the sooner you learn it, the better off you'll be.