Hi,
if you don't have vCenter server you can manage your host directly via GUI of vSphere client...download and install VI client from ESXi welcome page https://<IP address of your host> see picture attached
(With vCenter server installed you can also use vSphere Web client (based on Adobe Flash) which allows you to manage your VI through web browser ... note: Web client does not support direct login to ESXi hosts...)
For more info see:
Welcome screen:
vSphere client login:
For better picture about infrastructure manageability and access see this picture:
Hope this help...
Regards,
P.