How to select a Picker?
From the creation of a picking list's step, you'll be able to assign a picker to a picking list.
1- Once you've selected the orders you want to pick, select 'Create picking list' within the 'Bulk actions' button
2- You'll be redirected to the 'Create picking list' pop in. From there you just have to select the order picker you want to assign to the picking list.
Notice that selecting an order picker is not a required step.
To know more about how to create a picking list, you'll find the different step through the related article.