Let's say I made a dwarf character. In the dwarf traits I should add +2 constitution. If I pick Hill Dwarf as my subrace do I get both +2 constitution AND +1 Wisdom from hill dwarf trait?
You have to choose one.
Subrace is a trait from the dwarf race, with the following description (PHB 20):
Subrace. Two main subraces of dwarves populate the worlds of D&D: hill dwarves and mountain dwarves. Choose one of these subraces.
And yes, you get both bonuses (so +2 Constitution and +1 Wisdom).
(Note that there is a third official subrace available in the Sword Coast Adventurer's Guide, the gray dwarves, also known as the duergar (SCAG 104). This subrace can cast some spells innately, but suffers from sunlight, like the other Underdark races.)