How long does a Viburnum, Ninebark and Lilac flower?
How Long Does a Viburnum Bush Flower in Kansas City?
These are all pretty much spring flowering species, although there is some variation among cultivars. To have the most successful planting outcome, you'll need to start by considering the light where you want to plant and the soil type, as well as what plants grow well in your area. Find plants that are well adapted to your growing zone. You can get such advice from the county extension service, as well as the local botanical garden. https://www.gardeningknowhow.com/garden-how-to/info/what-is-extension-service.htm
Once you decide on what plants to use, spend some time learning about transplanting and preparing the site: https://www.gardeningknowhow.com/plant-problems/environmental/learn-how-to-avoid-and-repair-transplant-shock-in-plants.htm
Then all you have to do is google "where to buy...(whatever you've decided on)", purchase your plants, and you're on your way.