The various GNU/Linux distributions all use different policies when it comes to accessing scanners. Please refer to the information provided by your distribution for details.

On quite a few distributions you can solve this by adding yourself to a certain group, often "scanner" or "lp". There is probably a "Users and Groups" entry somewhere in your menus that let's you do that. You can also try the command line.
# adduser $user $group

or

# usermod --append --groups $group $user

or

# usermod -A $group $user

Of course, substitute $user and $group with values that match your situation.
You will have to log out and back in again to make these group membership changes take effect.