Parameters are passed into expressionengine tags as strings. I assume you are trying to pass in a php array into your parameter. In that case, you would need to refer to that particular tag's documentation to see how the values need to be passed in (e.g. pipe delimited "value1|value2" or comma delimited "value1,value2"). If you are using php, you can call the php implode function and that will return a string you can pass in.
$foo = array('hello', 'world', '!');
$bar = implode('|', $foo);
If you are not using php, then I believe you are thinking about the way expressionengine works incorrectly. ExpressionEngine does not produce arrays that can be used in your template that way.
If you are developing your own plugin, then you will need to do the opposite. You will need to fetch you parameter and explode it based on whatever delimiter is getting passed in.