1.)In Activating your cloudflare in a2hosting you need you change your DNS settings from the company providers example are namecheap , 1and1 and godaddy.
Change you DNS
2.)Then you need to wait for 48hours or 2days to fully configure.
3.) Go to your cpanel and click the sign symbol of the cloud.
notes: Sometime server downtime will happend so it is better to pause the cloudflare rather than deleting.