Customize fixlet for beginners

Hi everybody,
I started using IBM BigFix few days ago and now I am very interested in customizing fixlets. Unfortunately I don’t understand how parameters are passed from my description script to the action script. My javascript code contains this function:
{TakeSecureFixletAction( Relevance('id of current fixlet'), Relevance('id of current bes site'), "Action1", {}, { *name of param*=*value* } ); return false;
and I understood that my param is passed in the secure params list as name of param. But how can I use it in my Action script? I tried with this simple script:

setting a custom property of my clients = parameter name of param of action of client

but it didn’t work. Can someone tell me where is my mistake? Or if exists a link where I can find some informations for beginners? Thanks for the help.

So the relevance for seeing a parameter is at https://developer.bigfix.com/relevance/reference/bes-action.html#parameter-string-of-bes-action-string

The form of setting is at https://developer.bigfix.com/action-script/reference/client/setting.html

So this would require something like the following which does relevance evaluation (note the {} which designate the relevance see https://developer.bigfix.com/action-script/guide/substitution.html )

setting "settingname"="{parameter "testparameter"}" for client