We strongly recommend using single-file purge instead of full cache purge in most situations.
Purging the entire cache will mean all requests go back to your origin webserver(s) until the caches are full again. If you have many assets, and lots of traffic, those requests could be a flood.
Full cache purge may be appropriate, of course, and will immediately purge all CloudFlare-cached resources for your website. This will force CloudFlare to expire all static resources cached prior your action and fetch a new version when requested by visitors.
Find the Cache Purge option by going to:
Settings -> CloudFlare Settings -> Settings Overview
You can alternatively get to the cache purge for a domain by going to:
and within CloudFlare Settings, scroll down to Cache Purge
Clearing the Cache via API
You can also clear the cache through an API call. Review the documentation under sections 4.4 and 4.5 here.