Feeding young hamsters isn't too much more difficult than adult hamsters, but everything you feed should be fed with purpose. It is within the first 6 months of life that hamsters do the most growing so they must be supplied with a bit of a different diet than adults.
For protein- the best results are yielded when a hamster pup is fed a diet of 18%-19% protein. Any higher and the growth rate is slightly less, and lower and it's the same thing. After six months or so, you can lower the protein to 16%-17%
Fiber- this stays on the lower side in young hamsters, they only need around 10%-12% at this age, but it's crucial you raise the amount to 12%-20% as they grow older. Especially as they reach a year or so
Fat- you can give quite a lot of fat at this stage in life. It's been shown that hamsters can thrive on diets of up to 20% fat for up to a year so try to keep it under this amount. A better number to shoot for at this age is about 7%-10%
For vitamins, feed lots of turkey, eggs, tofu, cheese, low fat milk or soy milk, peas, and peanuts. These will all give good vitamins with the two most crucial being niacin and B12 at this age.
Good luck with your new little one, and if you ever have any other questions, please ask