how to create web service in netweaver 7.0?

Dear sir.

Firstly I'm new in sap product, and needs your help.

I downloaded netweaver 7.0 vmware on the sap site.

1. I want to create webservice on netweaver 7.0, and call this web service from other application.

2. If I create webservice on the another system, how can I call this web service in the netweaver?

Any guides or references appreciate.

Thanks.