To get a job in ISRO,  you will need to appear in the entrance exam conducted by them. You will have to wait for the job post by the organization.They are usually released in feb-march.

But do keep in mind, this is not a rule which ISRO followed every year.  The details regarding admission and procedure will be mentioned on the job ad.

It has few eligibilites, these might help you analyze better about your path to a job in ISRO.

1.should have completed either diploma or b.tech

2.more than 60% in b.tech(different for reservation candidates)

3.should be indian citizen

4.age should be between 21 to 30 years.

5.candidates in final year b.Tech can also apply(only if they can produce degree certificate at time of interview)

6.GATE score is also given huge importance.

This may help.

Happy learning!