I think you just emailed the same question to us? If so, a couple of suggestions for future reference: If you are going to email a question to our technical support department, please don't post the same question here, as it can result in a lot of duplicated effort--pick one destination or the other. Second, when emailing tech support, please be sure to include your RATS serial number with your email.
As for the question, the first step is of course to get the data read in. If you have no idea how to do that, please start by working through at least the first few sections of the "Introduction to RATS" book included with the software. That should tell you everything you need to know about reading in data.
In terms of applying the Bry Boschan algorithm, that is available in RATS via a pre-written "procedure" included with RATS called @BryBoschan.
Assuming you are new to using procedures in RATS, please see pages 32-33 of the Introduction for some general information on using procedures. You can find more on using procedures on pages 451-452 of the "User's Guide".
Next, open up the BryBoschan.src file (which contains the code for the procedure). You will find comment lines at the top of the file describing the syntax (options, parameters, etc.) and other details of the procedure.
I hope this will help you get started.