How can I define a specific separator to divide fields and values in my source?

It’s very easy! You just need to configure the parameters of your source and select the preferred separator, pipe in this case. BigML also lets you define a new separator if yours is not included in the standard list shown below. Simply select other and type in your desired separator:

If you prefer to use the BigML API, just type what follows:

All the parameters you can use are listed in this arguments subsection.