The Portugal international struck a fine brace to lead Real to victory in Cardiff, having started despite concerns over his knee.
Ronaldo admitted to being apprehensive heading into the encounter, but said he felt comfortable.
"I felt well. It was my first official game. I was a bit worried, I didn't know what was going to happen, but I felt very good," he said.
"The team helped me and I scored the goals that have given me more confidence. And I have to keep working to be better in the next games, but I felt comfortable.
"I didn't feel pain, and I feel good, and I helped the team to win this important trophy."
Ronaldo got on the end of a pinpoint Gareth Bale cross to score the opener on the half-hour mark before thrashing a drive past Sevilla goalkeeper Beto in the 49th minute.
The 29-year-old said Real were worthy winners of their second Super Cup.
"We knew that it was a difficult game, but we played better," Ronaldo said.
"We had chances to score goals. Sevilla had one also but it was because of our mistake.
"But we played better, with more intensity, we had more chances and we scored two goals. In my opinion, we were clear winners, and that's why we go back home with the trophy."
Real face Fiorentina in a friendly on Saturday before their two-legged Supercopa de Espana tie against Atletico Madrid.
