We also recommend that if you still have difficulty, you are welcome to contact us or seek professional help locally (the easiest place is to ask at a local lingerie shop).  Many department stores will often invite a bra fitting expert in their store, and believe it or not, the consultation is usually free, if you shop there.  There is also a lot of information on the Internet on how to measure your correct bra size and choose the right bra.  Most of the information is typically provided by online lingerie shopping websites. It is of course always a good advice to confirm your research with a professional. 

Assuming that you have already selected the tightness of the bra's back strap, when putting on a strapped bra, regardless of cup size, after first slipping the straps over your shoulders, lean forward at at least at a 90 degree angle to your legs. Then affix the back strap around your back and fasten it. Wiggle yourself slightly from side to side to get yourself centered in the cups and then stand up. This will place them firmly into the bra cup and assure they are where they are supposed to be.  This is really important because otherwise you will not get the support they need and the whole purpose of wearing a bra will be defeated. (Related:  Simone Perele Argentina lingerie)

Strapless bras are put on in much the same manner, but it is vital that the back strap is placed exactly where it is supposed to be before it is fastened.

If you are are still not perfectly fitted into the bra, you probably did not lean forward enough, the back strap was adjusted too tight or too loose (many women may have to try a different tightness when putting on a bra this way) or you have the wrong size, shape or cup size bra. Still, practice putting the bra on in this manner several times before making any final judgments.

Recommended links: Guide for lingerie shopping     Tips for men to shop for lingerie   Braless