Crankshaft timing gear help

I need help! So I took my old gear off to replace the crank seal. In order to take it off the gear comes off then the woodruff key will come out. To put the gear on do you put the woodruff key in the crank and then put the gear on, or do you instal the gear then the key? Some advice would be great lol! Btw it's a 06 sti
Thank you,
Ryan

 

Should it wiggle on or will I need to tap it on with a rubber mallet or something?

 

Thank you! I got it on!!