The male sperm is extracted by holding the male alive and making a slight incision with a razor blade at the under belly, close to the genital organ.
Then the under belly is exposed by removing the intestines.
Lying at the back of the under belly are two lines of sperm sacs, like the man's tumb.
Cut it out and wrap in a tissue to maintain the same body temperature.
Then depending on the type of fertilization you are doing, the sperm is prepared further or used directly by splashing the liquid on the eggs.
This is called wet fertilization.
You can also slice the sperm sac in a plate and add some spoons of saline water to "activate" the sperms.