If you are using a randomization algorithm outside of Castor, you can import the randomization data into Castor as well. 

Follow the steps outlined below:

1. Create a new field or fields which will contain the randomization allocation or other randomization data in your study forms - this can be for example a numerical field (for the randomization number) and a text field (for the randomization outcome)
2. Prepare a CSV file with the participant ids and the relevant randomization data represented as separate variables. If you haven't created participants in your study, you can do this on the fly while importing. 
3. Import the CSV file into the study

At the moment, it is not possible to import a randomization list in Castor that you would use to randomize in real time.