Here is a link to the Help page which explains the DNA confirmation process. Help:DNA Confirmation (wikitree.com)
Basically you need to write a statement for each person that shows how your DNA matches theirs and supports the relationship, for example, my confirmation statement for my father says
Paternal relationship confirmed by Gedmatch match of 3586.9cm between kits T248947 (Joe) and A340796 (Kathie) at a genetic distance of 1.
I was also able to confirm my father's parents (my grandparents) with a match to a first cousin, which looks like the following on my dad's profile:
Paternal and Maternal relationships are both confirmed by an autosomal AncestryDNA test match between [me] and L.W., her 1st cousin . Their most-recent common ancestors are James Parks and Mary Youngblood, the grandparents of both [me] and L.W.. Predicted relationship from AncestryDNA: First Cousin, based on sharing 1102 cM across 36 segments.