To find your measurements:
It is generally better to ask someone to assist measure you rather than trying to do this yourself.
To measure your BUST: You need to measure with a bra on and around the fullest part of your bust. Tape measure should be held firmly but not pulled tightly and you should be able to place a finger under the tape measure with ease.
To measure your WAIST: Stand in front of a mirror and measure all the way around. This must be on the smallest part of your waist where it's the narrowest.
To Measure your HIPS: Find the widest part of your hips and measure all the around, ensuring you go around the lower part of your bottom.