During this age of 4 weeks old, the pups will be spending more time away from the dam to play with each other while she gets a break from the ruckus. It is during one of these play events, once an appetite has been worked up and they are not close to the dam to attempt to nurse, that the mixture should be offered.
You'll want to have this in a very shallow dish that they can easily reach into. Offer this once on the first day. Having no experience with solid food, a puppy that is just being weaned may only lap at it and sniff it to investigate it and that is fine. Then going forward, you can serve it 3 to 4 times per day.
While you are paying attention to feeding the puppies, this will give the dam a good opportunity to have more time to herself. She will be very exhausted and in need of some alone time; much like a human mother who just needs to get away for a few moments to regroup. This step is also important for the weaning Beagle puppies to get used to having the dam away for periods of time and be more accustomed to your presence. During this time, handling them and speaking to them is part of the socialization that they need to prepare to be independent.