You can manage your DNS records via DNS Zone Editor. To add a new record choose the type of record as MX (or scroll to MX records section in the old interface).
If your domain is pointing elsewhere by NS records, your DNS Zone management is moved to the provider you pointed the domain to and should be managed from there.
What to use as a Name (Host)?
If you are adding MX records for your domain, insert @ as Name.
If you are adding MX records for your subdomain, insert the subdomain’s name as a Name, for example for subdomain support.hostinger.com you should insert support as a host.
What to use as a Mail server (Points to)?
Mail server is for MX records to which you want to point your domain.
What to use as Priority?
Priority for MX records is defined by the mail service you would like to use. For Hostinger free email services, for the mx1 record, you should use 5 as a priority and for the mx2 record use 10 as a priority.
What to use as a TTL?
Default TTL value is recommended.
How to edit or delete MX records?
In the list of records you will see these buttons:
Button to delete record completely
Button to edit record
Any DNS Record changes trigger propagation, which can last up to 24 hours to fully propagate.