Its easy:....
Just Program>Edit design and in the window that comes up you can cut and paste the parameters into the model file.
Here's the deal.. Open up a part that already has the parameters added, use Program>Edit design>from model to find the user defined parameters, copy all the lines between input and end input.
Now go back to the file you want to modify and do the same, only now you paste into the part file. The new lines will go between the input and the end input lines.
Say yes to accept the changes and regen the part,
add the parameters as prompted.
If you have alot of files to do you can create a text file with the lines in it and the file is always there for futre editing.
Skuld ...^_^