Clear out the initial single blocks and work your way over to the locked in pieces. Releasing the locked pieces will be helpful in getting the pieces down the left and right side columns and allow you to score more and get more pieces on the board. Since you need to make 13 striped candies, this is also a great idea to remove the locked in pieces and score something you need anyway.
Thanks to Matthew Dean
Patricia Frederick’s Tips for Candy Crush Level 146
Keep clearing out the blocks as you move downward to create more room for candies. A color bomb/striped candy combo will collect the striped you need, so focus on striped/wrapped combos to collect the colors.