i have checked this page, but it didn't seem to tell me where i should put the plugin file, and what the file extension should be.
my os is arch linux.

@4ZZ4 whatever-plugin.tcl
The filename has to end -plugin.tcl.
You can put them in any search path that Pd will find as it starts.... so....
Pd/bin
Pd/extra
or any other that you have set in Pd preferences path.

To stop it working just move it somewhere else and restart Pd.

To create them you either need to be a Tk/Tcl wizard or rummage around in the Pd/tcl directory and stab around in the dark........ looking for clues on the web as to what it might mean.......
David.

@4zz4 here are some examples: https://forum.pdpatchrepo.info/topic/10943/a-little-pd-mod