Figure out your power points from each class, and then add them together.¹ For the “high ability score” table, you use your manifester level for each class—not your total character level. So since a 6thlevel aegis has 9 + 3×Int power points,¹ and a 1stlevel vitalist has 2 + ½×Wis power points,¹ a 6thlevel aegis/1stlevel vitalist has 9 + 3×Int + 2 + ½×Wis power points.¹ With Int 18 and Wis 16, that’s 9 + 12 + 2 + 1½ = 24½ = 24 (cuz we always round down).²
You only have one pool of power points and can use that for anything you use power points on—aegis customizations, vitalist powers, and so on.

_{This is all assuming you don’t have any bonus power points from your race, feats, items, or whatever. If you do have any of those things, those get added after figuring out your base power points from your class and bonus power points from high ability scores. So if you are naturally psionic and have 2 bonus power points from your race, a 6thlevel aegis has 9 + 3×Int + 2 power points, a 1stlevel vitalist has 2 + ½×Wis + 2 power points, and a 6thlevel aegis/1stlevel vitalist has 9 + 3×Int + 2 + ½×Wis + 2 power points (not +4 at the end, which you’d get if you added the +2 to each class and then added those together). Also, if you have bonuses to aegis and/or vitalist manifester level, you might have higher multipliers than 3× and ½×, respectively, since those numbers are based on your manifester level in each class.}

_{The table for the bonus power points from high ability scores lists just “1” for the bonus at 1st level and a score of 16—that’s because the numbers in the table are rounded down. The formula is ½×ML×ability modifier, so ½×1×3 in this case, for 1½. It doesn’t really matter here.}