Command search path is just a variable - $PATH.

When you echo $PATH variable you will see a list of directories that should be searched anytime a user types a command.

echo $PATH
Printing contents of the $PATH variable

$PATH variable is user specific. root will have different value of the $PATH than ordinary user for example.

So how to extend path with a directory ?

export PATH=$PATH:/somedir

If you echo $PATH again, you will see that somedir has been added to it.

If you want to persist this, put it in .bashrc file.