in order to get ho-oh, on collisuim, u need to do these things:
1) catch and Purify all 48 shadow pokemon (if u missed one then ur in trouble and may have to start again)
2) Enter Battle mode and register your team of 6 from the STORY/SCENARIO mode.
3) Do the mt battle challenge in either 1 on 1 OR 2 on 2
4) Beat all 100 trainers
5) After you have beatn all 100 a message with ho-oh will say: 'The blessing of Ho-oh has arrived for the master OR revival of Battle' then it will say 'Ho-oh is sent to your PC'
6) You'll return automaticly to the main menu when uve done the challenge and after your coupons have been counted.
7: Go to scenario mode...go to any PC and Ho-oh should be there, Lv70, ready to be used.
I hope this helps