Power Query ; Custom function to work on a list

[Dicken]

Hi,

I have made a custom function to work on a list and insert a range of values, I have not worked these into the function yet,

the fucntion in based on this

let rc = List.Count( Source ) , 

check = rc / grupe = Number.IntegerDivide( rc,grupe) , 

n = ( Number.IntegerDivide( rc, grupe ) * insertN ) + rc , 

slist = { grupe..n } , 
altlist = List.Alternate( slist, ( grupe + insertN )-1, 1,1) 

in if check = true then List.RemoveLastN(  altlist, 1  ) 

else altlist

and the list.Accumulate to insert rows at the above positions,

List.Accumulate(  Altlist , Source, (S,C)=> List.InsertRange( S ,C, insert ) )

But I have made a basic function not incorporating the rows to insert or grouping by number, but I can only get it to work
by type it in so; Function ( list) , but can't figure out how to use the options to enter parameter ; invoke dialog box ?
is there a way to select a list as you would a table? I don't know whether to use ( func name as list) => or just leave it out ?

I have attached work book with example and function,

Richard.