How to mount header bracket for garage door opener to concrete wall?
Mount a 24" piece of 2x6 up there with four 3-1/2" lag screws and 4 2" lag  shields, one in each corner.Then screw the bracket into that with two 1-1/4" lag screws. Use 3/8" lag screws for the header and bracket. 

Center the 2x6 over the hole in the concrete, Screws should be about 1" down and over or 1.4" diagonally from each corner. Washers are a good idea. You're going to need a hammer drill for the concrete since you'll have drill 2-1/4" deep for each lag shield.The drill size will depend on the actual lag shields purchased.