You need a crank made for a 73 mm bottom bracket shell. Tiagra is a road crank and made for a 68 mm (or 70 mm if Italian ) shell and the spindle isn't long enough for a 73 mm shell. You need an MTB crank/spindle made for that shell width or, as Andrew noted, have the shell faced down to 68 mm, which won't be easy.
Originally Posted by
Leisesturm
. Edit: it would appear that Tiagra cranksets need HollowTech II bottom bracket cups. I assume you already have a spindle? (24mm)
Hollowtech II cranks have the spindle built into the driveside crank arm and they aren't changeable. The OP needs another model crank with the proper spindle width, either an MTB Hollowtech II or a suitable square taper compatible crank.
To the OP: a press-fit bottom bracket will not work with a threaded bottom bracket shell. You need the correct crank.