Not as much as you think.
Obviously, they need to keep dinosaurs out of their crops, but hunting usually takes care of that. Viking means bows, spears, and traps, which means dinos don't stand a chance in the long run.
Settlements will likely be build defensively, but they did that often anyway. Log walls keep out dinosaurs as well as clever monkeys. Islands, bluffs and other defensively positions are chosen for defense from humans but work just as well against dinosaurs.
Dinosaurs are not movie monsters. They will be driven off by humans just as well as any other animals. Humans are really really good at killing large slow armored animals. Small dinosaurs are the only thing that will a consistent bother but then no more than wolves or bears are. Anything big wandering too close is just a feast waiting to happen. Do expect livestock to take a big hit at first, and still run into occasion attacks for long time afterwards.
Far outside settlements is a different story. Out in the wilderness, running into a a large dinosaur predator will be a real danger -- more than running into a bear since humans are large enough to give bears pause, but a t-rex may just see an easy meal. That said a group of humans acting together can kill just about anything, so that will be less of a problem as time goes on. A t-rex will cause problems until they get a team together to hunt it, but humans should quickly whittle down their numbers.
Worse as egg layers, dinosaurs will be vulnerable to humans wiping them out, since they can't really move the eggs away. Only if you have migratory dinosaur herds will humans settlements suffer any significant disruption. Large herd can literally overwhelm the ability to hunt them, but that is onlyan issue if they migrate directly through the settlement. Otherwise, back to easy meat.
Now the water will be a bigger problem. There are several large predators who might see a Viking ship as prey. worse from below they would even resemble prey.