I was on the train from Paris to Barcelona in November. Search for your trip at
https://www.sncf-connect.com/en-en/train-ticket and
https://www.rome2rio.com/map/Disneyland-Resort-Paris/Barcelona#r/Train-via-Lyon
You will find several train options, choose whichever fits your schedule best. I suggest pricing an Uber or equivalent from the resort to the departing Paris train station as an option, especially if you opt for the SNCF/TGV inOui train departing from Gare du Lyon as there are no direct trains from the resort station. Depending on your date of travel, there is a Renfe train option from the closest train station to the resort to Barcelona with a connection in Lyon, though it may be more expensive than the direct train from Gare du Lyon.
Realize that the resort is not close to downtown Paris. You will find RER local trains which take about 35-40 minutes each way. However, note that there are occasional interruptions. During my trip, two of my friends went to Paris for the day and on their return the train abruptly ended half way due to an emergency (all trains on that route stopped there for many hours, until the issue was resolved). So, I drove out to pick them up and it took at least 45 minutes each way for me to get them. The likelihood of that happening during your trip is low, but thought it worth mentioning.
Are you traveling for four days total, or four days in Paris? If four days in Paris, my main suggestion would be to not stay at the resort… in my opinion, it is just too far away to be able to fully enjoy the city for more than a day.