If you type a command into Terminal, where does it look for the program you’ve specified? The system looks in a set of directories established in your PATH statement. A number of directories are specified in the default path as soon as you boot BeOS. But what if you want to add to that list?
To see a list of directories comprising your current path, type $PATH . To add to that list, type export PATH=/boot/NewDirectoryName:$PATH. Now check your path again, and you’ll see that the new directory has been added to the list.
Want to make the change permanent? Just add the export line to your /boot/ home/.profile or /boot/home/config/boot/UserSetupEnvironment (preferably the latter).
After first editing either of these, you’ll need to have them read back into memory:

source ~/.profile
source ~/config/boot/UserSetupEnvironment