Puppies don't need much encouragement to remain active, but there are a number of things you can do to ensure they stay healthy! When you first get them, make an appointment with your vet for a new puppy check-up, so that you can have them checked over and ensure that they're in good health. All puppies should have their first vaccinations at around 8-9 weeks old, and their second batch at about 12 weeks. Until you've done this and had them microchipped you'll need to keep them indoors, so try to find ways of letting them burn off energy safely!
Dogs need plenty of exercise, and your puppy will be no different. Make sure you're taking them out for walks as soon they're vaccinated, but keep them short and regular rather than going on long afternoon strolls - you might be excited to take your puppy out into the countryside, but long walks will tire them out easily. Toys you play with at home should also help to keep them active - pull toys and balls are the best option to get them running around in the garden.