How to run ns2.26 tcl script

Hi everybody..

I am a newbie in ns-2. I really need help to run my project. I have succesfu
lly finished installing ns2.26. The problem is, when i was trying to run any
 example from the file such as example.tcl, it has returned an error message
 such as "command not found". I have tried all differents kinds of command s
uch as:

./ns example.tcl, ns example.tcl, $ns example.tcl, ns2.26 ns26 example.tcl

and many more. according to what i have learn so far, the code to simulate t
he script in ns2.26 is just "./ns <filename>"

am i right?? Is there any other command or i have type a wrong command? anyb
ody can help me on the problem i am facing? thank you in advance for your he
lp.