By default 'Meet Now' behaves in the exact same way as 'Personal Room'. And if you have the option, you may choose to use your 'Personal Room' for all instant meetings. However, 'Meet Now' offers configuration options that aren't directly available to 'Personal Room' (pay attention to 'meeting type' and 'custom meeting templates').
To change the default meeting type for 'Meet Now' to Training Center sign in to cwru.webex.com and choose Setup > Preferences. Choose "Training Center Training 1000" from the "Meeting type" selection menu and then click Sav