The spaceship that the astronauts are in has a cylindrical shower stall in the spaceship.
The astronauts just step into the on board shower and take a shower like you normally would at home on earth.
But since gravity doesn't exist in space the water droplets float around in the shower instead of going down the drain.
As for the bathroom and toilet the astronauts can either urinate into a long tube with a vacuum system sucking away the waste or they can sit down on a special toilet in the spaceship to get rid of the waste.
Some astronauts may also use a disposable adult diaper on board the spaceship even though the diaper is called a maximum absorbency undergarment in reality the undergarment the astronauts wear is just an adult disposable diaper.