How to mate two different sketch point?
If they are in two different part or one in assembly and one in part, then select them and apply a coincident mate. Make sure they are free to move before your apply the mate.
The two Sketch Point are in one assembly.
I deleted the coincident mate of the two sketch point because of some modifications then I tried to add again the coincident mate.
I edit the sketch of the other part to select its sketch point then how to select the other Sketch Point in other part?.
Make sure you've set the sketches to show (expand feature tree and set the sketch to show in which points are there) and then under view menu, sketches are set to show.
If you really mean mates, then follow Deepak's suggestions. Don't edit the sketches, just make them visible.
If what you really had was a coincident relationship between a point in one sketch and a point in another, then make the first sketch visible, edit the second sketch, and add a Coincident Relation by control selecting the two points.
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