If you appeared in Atma exam held in Feburary then you can definitely take admission on its basis and if you are appearing in upcoming atma exam then mostly colleges won't accept that as admissions are already closed in all the top B-Schools but still there are some colleges which will accept it's score.
You can get the list of accepting colleges in your form of Atma, when you'll be applying there is a list of accepting colleges so you can go through that.
Also I'll suggest to prepare for CAT 2020 as it's just 3 months ahead and target top 50 colleges of India as in Atma exam there's no top most college which accept it's score, only welingkar Mumbai and welingkar banglore accept it that too of September and February attempt, now admission are closed in welingkar college too.
Conclusion:- you can get admission though upcoming atma exam in mba this year itself but I'll suggest you to go for cat and other exams for taking admission next year.
To know more about atma and it's accepting colleges list, you can visit the following link:-
I hope this information is helpful for you.
All the best for your bright future ahead.