vhdl library help

This is how you declare and use packages:

package my_function_package is
  --put constants here
  --put function/procedure declarations here - note: this is not the entire function
  function do_stuff return something;
end package my_functions_package;
--the body is where you put all the function code
package body my_function_package is
  --this is where the code actually goes
  function do_stuff return something is
  begin
    --do stuff
  end function do_stuff;
end package body my_function_package;
--then in the file you want to use the function
--unless you have specified my_library, replace it with work
library my_library; --not needed if library is work
use my_library.my_function_package.all;

architecture rtl of some_entity is
  --function goes here
begin
  
  process(clk)
    --function goes here, you can also declare constants and variables here
  begin
    --something
  end process;
end architecture rtl;