I like to use a small bead of caulk then draw my index finger which I moistened with a little water and draw it down along the bead at a 45 degree angle. If the gaps are wide, you can repeat this process daily until the gap is fully sealed with caulk. Build it up little by little each day.
Silicone is very tricky to work with. I find this method the best. Tried and true.
If you do it right the first time, the caulk joint will last for years.