You can use any cream you want, as long as it adds moisture, smoothness, and shine. You can even use a small amount of conditioner, if you want. Apply the product all over you hair, but focus it on the ends. You're hair should be damp enough so that it is still wet but no longer dripping. A side part would look especially cute with beach waves, but you can do a center part too. Use the handle of a rat-tail comb to make the part even and clean. You will need vertical two sections on each side of your hair. If you have longer hair, you might be able to get away with just two sections, one on each side of your head. Secure the buns with small hair ties or bobby pins. Make sure that they are secure and won't come out. For tighter waves, twist each section into a rope braid first, then twist it into a bun. If you created a side part, consider leaving a small wisp of hair at your hairline out of the buns. This depends on how well your hair holds a curl. It also depends on how tight your want the waves to be. If you want really loose or relaxed waves, you can skip this step. How long this takes depends on how thick and porous your hair is. It could take an hour or it could take overnight. You can speed things up by using a hair dryer, but you need to be sure that your hair is dry inside too.  Keep in mind that using a hair dryer will not ensure that the inside of the bun is dry. If you want to speed up the process, it's best to sit under a hooded dryer. If you left a wisp of hair out of the buns, twist it into a delicate rope, then drape it behind your ear. Your hair should have taken on a loose, wavy shape. Again, your buns must be completely dry before you take them out, otherwise the waves won't hold. If you coiled the wisp of hair behind your ear, you can uncoil it now. Your hair is likely clumped into two big waves (or four if you did four buns). Run your fingers through your hair, shaking them a bit. This will help break the waves up into smaller waves. It will also help add volume and a messy, beachy texture. This really depends on how well your hair holds a curl. If you have thick or curly hair, you may not need any hairspray; if you have straight or fine hair, a light misting may help the style hold longer. Here are some other finishing tips, depending on the look you want:  Spray your hairbrush with sea salt spray, then comb it through your hair for volume. This will make your hair appear fuller. Apply some dry shampoo to the roots for more texture. Tease your hair at the crown for even more volume. Tame flyaways with a styling cream, serum, hairspray, or a little bit of conditioner.

Summary:
Apply a styling cream to damp hair. Part your hair as desired. Divide your hair into four sections. Twist each section into a mini bun. Mist your hair with a lightweight hairspray, if needed. Allow your hair to dry completely. Undo the buns once they are dry. Gently break up the waves. Set the style with hairspray, if desired.