Take the Trans Canada Hwy 1 West to Hwy 75, the exit for Carbonear (Exit 31). Stay on the main highway, if you take any of the exits, you will end up on the coastal road, which will work, but will take much longer (50 km/hr).
At Carbonear the highway ends. Continue on the main road until you get to Victoria. You now have a choice to continue on Hwy 70 (Conception Shore) or Hwy 74 then 80 (Trinity Shore). Each is nice, and will get you to the same place in the end. The drive from Carbonear to Grates Cove takes about an hour.
If you choose Hwy 74, you will come to Heart's Content. Take Hwy 80 North.
Both 70 and 80 will lead to Old Perlican. There is an Irving Gas station at the intersection. Take Hwy 70 to Bay de Verde (turn right if you came on Hwy 70, go straight if you came on Hwy 80).