Hi @katalontstr ,
Due to the incompleteness of the current documents, the Customer Support team has just published another instruction here to help you guys overcome the current situation. If you have any problems following this instruction, please comment on the post, and we will be there to support you too. 
[Product Support] One-time setup for iOS Mobile testing Successes
In addition, @Elly_Tran, Please help navigate other users who are having trouble setting up iOS testing to the above post also. I and c @linh.nguyen from the Customer Support team will be staying there for a few days to support any other related issues. Thanks! 