Where do you put concealer? Where's the best place to get it?

I want to wear make up but don't know where to put concealer.Where do you put concealer? Where's the best place to get it?
you blend concealer over scars and blemishes to mask them so they're not as easily seenWhere do you put concealer? Where's the best place to get it?
mostly under eye.
under eyes, around my nose (where it can be reddish) and on blemishes--if i have any.
concealer is used to cover blemishes. It goes under foundation which is used for all-over coverage.