Target Field's address is:

1 Twins Way,

Minneapolis, MN

55403

It's in downtown Minneapolis, north of Target Center, which doesn't help a lot, as that's a very large building.

Better to look for Parking Ramp C (or the nearby Underground Music Venue) to get closer to where you'll enter on foot.

The trick to entering Target Field (for large concert work) is to get down to the level where the trucks park and then walk in (yellow lines) at the north east side of the stadium, at the same level as the field.

If you are driving, it's suggested to first get to the intersection of North Washington Avenue and North 3rd Avenue. Bear in mind North 3rd Avenue is a one-way street.

The green arrow will take you to the entrance of the C Ramp.

Park there and walk to the North end of the 'C' ramp (4th Street North Parking Garage/Transit Building, 329 N 3rd Avenue, Minneapolis, 55401), take the elevator to the lowest level, B, and you will exit at the level of what used to be the truck parking lot for the stadium. Follow the yellow arrows to the check-in area, located at the pink star.

The red line is also North 3rd Avenue, again a one-way, but the opposite direction of your walk, for cars going south-east from the intersection with N. Washington Avenue. 

You can take the light rail to Target Field and then following the red arrow, cross the street and walk north-east on North 3rd Avenue towards the C Ramp, also known as the 4th Street North Parking Garage/Transit Building.  Following the yellow line, there is a wide ramp going down to field level, to the pink star, which is the check-in area.