After giving CAT, you will have to wait for results. Results will probably be declared in one month. Once the results are declared, either on the same day or within a week or so, looking into your percentile and whether you have met the cutoffs of different institutes, all the IIMs and other colleges which take CAT scores and to which you have applied, will start sending you calls for further rounds of WAT(Writing ability test), GD and PI. For the IIMs to take your CAT score, you have to only apply for CAT but for other institutes(other than IIMs), that take CAT score, you have to apply for them separately on their official website prior to giving CAT. The forms of these colleges are opened for registration, after one or two weeks of announcement  of CAT registrations. Whichever college you wish to apply for other than IIMs, you can apply. 

Some of the colleges which take CAT percentile are

IMT, Ghaziabad

IMI, New  Delhi, Hyderabad, Kolkata 

SPJIMR, Mumbai 

IITs

MDI, Gurgaon 

FMS, New Delhi 

IRMA, Gujarat 

MICA,  and many more 

For these above mentioned colleges you need to apply separately too other than filling the CAT registration form. Few colleges like IIMA, MICA can take their own exams too other than CAT to check your competency  in certain domains. 

For more colleges you can refer to :

https://bschool.careers360.com/home

After CAT results and calls for GD-WAT-PI, which are held in February - March - April, final results are declared in April - May post which you have to pay fees if first term and take admission in college where you got final shortlist and of your choice among those final shortlists.