First, log into your Namecheap account using this link: Log in here
Once you're logged in, you will need to add a CNAME record and an A record for your domain.
These articles from Namecheap include screenshots showing how to navigate to the "Add New Record" area for your domain:
1. How to add a CNAME
2. How to add an A record
Follow the steps in the first article to add a new CNAME. When entering your new CNAME info, put www in the Host field, and custom.zarlasites.com into the Value field.
Then follow the steps in the 2nd article to add a new A record (it will be very similar to the CNAME).
However, for the A record, put @ in the Host field, and 109.105.219.109 in the Value field.
Lastly, it is possible to have multiple CNAME records, and multiple other types of records, but - please note - you are only allowed one A record.
If you see any A records (sometimes shown as AAAA records) that exist other than the one we instructed you to create, please click the delete icon next to those other A records.
You will most likely have some A records you need to delete, so make sure to do this step as well.
When finished, contact our support team and we'll make sure all the settings are correct, then push your domain live for your website.