Load OS to template

Hi gurus

as you can tell for mey previous post, I am still learning the vmware worls. so go easy on me

I have setup a vcenter and now I have vsphere to centralize manage my env., now I know that we can deploy machines base on a template , master and all that good staff, what I dont have a clue to do is how to load into vsphere a os( e.i windows 7 32 bit) machine so I can use it later to clone or link future VDI machines  with that image,iso.

so if a template is a vm

how do I create a VM ( windows 7 32bit) that I can later use as a template, how do I go doing that.

Thanks a bunch gurus