I am using jmeter to test a javascript application

I am using jmeter to test a javascript application. I need to create a different thread with a unique session for each user. Because in my application you can only have one login per user at a time so putting 100 times the same user I will not get to any conclusion. I have created 40 users user0,user1....user39 with the same password is there a way to automatically create simultaneous threads for each of them?