start by making sure that the vehicle is all the way in park - even if it looks to be in park already, give it a firm little nudge.
If that doesn't work, the lock cylinder housing and/or steering column and/or shift lock mechanism will have to be inspected (possibly removed & inspected)
RepairPal Certified shops can diagnose and repair your 2013 Kia Soul. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.