SL6 x64 Intel Chip - installing & running Fritzing

In Windows this would be true as Windows searches your current directory as well as the path. Unix doesn't, so even if you are in the correct directory unless the command is in your path you will get the "not found" error. The ./ in front of the command indicates "look in my current directory "." (with the following slash saying it is a directory. Your problem with sudo is that your account isn't in the sudoers file (typically /etc/sudoers but your system may vary). To change that you will need to log in as root as Smilliken suggested. It looks to me as if you may have more problems than this though. From the complaints about kde-config not found I suspect you may not have the kde desktop installed and Fritzing may want it (with the reminder I'm a Windows Fritzer and thus may be wrong here ). Log in as root and fix up your sudoers file and try the install as root and go from there is probably the best plan. If it wants KDE and it isn't there it will complain I'm sure.