Doing a variety of stretches will get your flexibility improving pretty quickly.
Make sure you practise movements like but to floor squats and over head squats; OHS help develop great flexibility all over.
Start and finish workouts with some dynamic stretching (ie, leg swings). Do the majority of static stretching after a workout when your body is warmed up. Also try and incoperate PNF stretches as much as possible after workouts, having a partner will give better results, but you can do some PNF stretches using your own body weight as resistance.
Make sure you put the time into stretching, the more you do the more flexible you will become. So after workouts dedicate around 15-20min of stretching time.