This is exactly how CloudFlare works.
First you need to sign up for CloudFlare, add your site and get it scanned. Make sure your site is currently live, else CloudFlare cannot catch your DNS servers. Once the scanning is done, CF will automatically get your DNS details. Confirm them and add your site. After that CF will give you two NS (nameservers)
Now, login to your namecheap account, get your site DNS settings, replace those NS that you added from your hosting company with those from CF. Wait for a few hours and you’re good to go.
Now your site will be routed via CF DNS servers and you can save a good number of Bandwidth. Moreover, it can help you detect some spams. You can also speed up your site with the help of CF caching. Read more about here Website Performance & Optimization | Cloudflare