Yes, you’ll have to follow this @ashish_shah
My question is, where exactly do I do that selection?
Since you mentioned earlier that, I can opt for quarterly filing, which will happen in APR-2022. So will I have to do selection then or do I have to do it now?
Hi @ashish_shah, you’ll need to log in and then click on Services->Opt-in for quarterly return.
Post that, select the financial year from the drop down list. And you can choose ‘quarterly’ accordingly. Let me know if you continue to face an issue. 
Hi @Yash_Kaviya , I just went there and it automatically selected monthly for me.
There was no Quarterly option for Jan to Mar 2022 period.
Hi @ashish_shah, because you registered on the portal in this current quarter, you would not be able to opt-in for quarterly return. Monthly is the default option for the quarter you registered. However you would be able to choose the quarterly return option from April onwards, which is the next quarter.
@Yash_Kaviya
Also one more question,
If say for the services provided in FEB-2022 month, I raised invoice in MAR-2022 and got paid in MAR-2022, then would my GST filing for FEB-2022 month be NIL?
@ashish_shah, yes if the invoice is raised within 45 days of the completion of service. Otherwise, the same should be shown in February.