Pollen is collected from flowers, that counts as the protein ( amongst others ) in the bees diet. They carry it back to the hive on their back legs where it is mixed with honey to make royal jelly to feed brood.

Pollen can be fed back to the hive in late winter to encourage early brood development to enhance your spring harvest of honey. You should only feed back pollen that has been collected from that hive otherwise you run the risk of spreading AFB. To do this you simply put your pollen collected from the previous summer and grind it fine in a morter and pestal then present it to the bees in a container with high sides ( they can be messy with pollen ).

Another way is to give them artifical pollen paddies. I dont do this myself but below is a recipe if you want to give it a try;

1.5 cups ( 225g ) fat-free soy flour
1.5 cups ( 340g ) granulated sugar
.5 cup ( 28g ) Brewer’s yeast ( not for a bread maker )
1.5 cups ( 375ml ) Sugar Syrup (2:1) or your honey

You can also use regular soy flour. Add water as needed to mix. In very warm climates it may be necessary to add an oil to prevent drying.