I´m really new at this so i apologize if the question is dumb. I tried to change the size of a .png using GIMP but when I try to save the darn thing i get a error "couldn´t create file". what is wrong? I´ve heard something about permissions limiting certain action. could it be that?

yes, it could. if you made the file first as root, and now are trying to save over it as a reg user, youll get permissions error. (or vice versa)
it could also be taht you ran out of space on your partition

From a basic Linux install you'll only have permissions as a normal
user to save to /home/<username> which is great for the purpose
of security.

So, assuming you have /home/arsongt as your directory, then save
the photo there. If you want to move it somewhere else, either
create a new directory, or login to a console as root and move it
with the command ->
~# mv filename /new/location/you/choose

What version of GIMP are you using? Can you print with it, and if
so, what service do you use to print? I'm running GIMP 1.3.23 and
I can't print with it at all.

A couple of things might be happening.

First, if you didn't create the PNG file (i.e., you are not the owner) you might not have write permissions on the file. No write permissions and you cannot overwrite it. Something to try: when you save the file, give it a new name. For example, if the original image was "image.png", save it as "bigger-image.png".

If you still cannot save the file even when giving it a new name, the directory where you are attempting to save the file does have permissions that allow you to write to it. Something to try: when you save the file, specify a different directory to save it in. Unless your system has been configured very strangely, you should be able to save it it "/tmp". Everyone on the system should have write permissions on "/tmp".

Since it appears that the whole permissions thing is new to you, here's my nickel tour of UNIX/Linux permssions.

In general, Linux (like UNIX) categorizes access to resources (files, directories, devices, etc.) according to three types: user, group, and world. If you created the file, you own it, and you access the file according to the permissions for the user. Other users on the system can be lumped into a groups according to, say, functions they perform on the system, different development teams, etc. Users who are members of the group that owns the file would have the access specified by the file's group permissions. Users that are neither the owner nor in owner group are allowed to access the file according to the "other" permissions. You can see the different permissions on the file by entering a command like "ls -l image.png". You'll see something like:

which means that the file is owned by the user "joe", the "devel" group, is 12,345 bytes in size, etc., etc. The stuff we're concerned with is that bit at the beginning of the output. It represents the permissions on that image file. Regular files will have a leading "-" in this string; directories will have a "d" in this location (there are other types of objects on the system and they'll have different characters in that position). Then there are three characters that represent the "user" permissions, three more that represent the "group" permissions, and the last three are the "other" permissions. In my silly example, "joe" can read or write this file ("rw-"), members of the "devel" group may only read it ("r--"), and everyone else on the system is not even allowed to read the file ("---"). If this was a program, it would normally have "execute" permissions set which would be seen as an "x" in that string so you might see some files having permissions like: "-rwxr-xr--".

Read up on the "ls" command and the "chmod" command to learn more about the various permission settings and how to change them.

Have fun,

Rick