Get a big mirror at home, watch videos of guys who pose great, find pictures of the best physiques of all time in each pose, print them out and tape them around the edge of the mirror, and stand in front of it once a day for at least 5-10 minutes flexing and comparing yourself to the pictures.
Don't fall into the trap of trying to look artistic, doing "smooth transitions", making ballerina spinning movements, trying to do too much as if you can change what your body looks like. The biggest mistakes guys make posing is overthinking it, overdoing it - especially when they can't just stand there and flex for 30 seconds without shaking, losing balance, etc.
Your presenting your strength. Your not a dancer, your not a stripper, your not a goof ball, or a rapper, or a ballerina. Your a mountain of ripped granite that can press a car off his chest, jump to the top of a building with a tank strapped to your waist, curl a stallion with one arm. Your a middle linebacker that just knocked somebody's head off, a gladiator and a king, taking your place on the throne.