This is usually done outside over an intense heat such as a propane burner. That's the only way to cook this much food all together!
Fill a large steamer pot halfway with water.
Add crab-boil seasoning.
Add halved lemons.
When the seasoned water comes to a boil, add redskin potatoes and onions and boil for 20 minutes; then add 2" slices of spicy smoked sausage and boil for 5-10 minutes.
Add the corn and boil another 5 minutes.
Then add the shrimp. Cook for 3 minutes. (Don't wait for it to boil again or you will overcook the shrimp.)
Drain, and pile on a table.