How to make Vinland not just settled but also grow into significant power in New World?
And, evenmore, becomes the center of Viking colonial empire?
Thanks in advance!
Getting Vinland to survive and thrive is one thing. But it would take centuries of steady population growth, constant access to the the sea, successful campaigning against expansionist American tribal groups like the Iroquois, and it will certainly need some level of contact with Europe, mostly via Iceland, to not lag completely behind in tech-development. One way of doing the latter would be to trade native crops and plants to Europe before anyone else.
After they are able to keep a strong-enough presence in one or two areas of Newfoundland, they should always make sure that further settlements should stay close to the coast or an estuary. Mastery over the water would be one advantage over possible native enemies. They also must try to keep hold of their knowledge of iron-smelting, and keep as many horses as well. Perhaps some horse-breeds from France and England would have made their way to Norse America via their trading ties with Iceland.
And, if they could stay secure enough in their position and relatively unified early enough, see that they could find the economic motivation to trade far beyond their geographic position as far as the Caribbean, central and South America. If somehow they could establish contact with the Incas before the Spanish or whoever start setting up colonies, so they could bring the potato to Vinland, that may boost their demographics long-term.
I would say that 'going Viking' won't always be the best option, as they should be traders first and colonizers second. Their area of settlement should stay largely within the Canadian maritime provinces, with the odd trading emporiums as far as the Great Lakes region and, later, the Caribbean Sea.
Vinland surviving the its first century and becoming a regional power are two different things. You'll really need to plan ahead, here.