What do you do after the buried relic in red rescue team?

If your talking about Pokemon Blue Mystery Dungeon, then you have to first buy the southern island friend area. The next morning there will be a cutscene that will tell you what to do.

If you mean Pokemon Mystery Dungeon, then you must first get the friend area "Southern Islands" from Wigglituff. Then you have to go into the square and a cut scene will tell you what you have to do.