If the job posting is on their website, tou will receive an auto-generated email for online assessment very shortly after you submit your application. You are required to complete the assessment within 3 days from the date of receiving, so make sure you have the time to finish it. The online assessment have some parts (you'll get the details from the email). In short, make sure to prepare for :
1. Competency assessment (either multiple choice/long-answer/video)
2. Behavioral event interview (STAR)