How can i set the policy to block the share folder access on some systems?

SEP version 12.1.5

You need to move that system particluar SEPM group and apply firewall policy

The following ports are associated with file sharing and server message block (SMB) communications:

• Microsoft file sharing SMB: User Datagram Protocol (UDP) ports from 135 through 139 and Transmission Control Protocol (TCP) ports from 135 through 139.
• Direct-hosted SMB traffic without a network basic input/output system (NetBIOS): port 445 (TCP and UPD

See Below articles provide how to enable sharing ,You can block as per articles

http://www.symantec.com/business/support/index?page=content&id=TECH170110

Symantec Endpoint Protection Manager - Firewall - Policies explained

How to block any website access?

These are the guide to block website

https://www-secure.symantec.com/connect/videos/allow-and-block-websites-using-symantec-endpoint-protection-firewall

Blocking a Website using Symantec Endpoint Protection

How to Restrict Users to Specific Web Sites by Creating Firewall Rules for Managed Clients

You Can Easily find all sep related query in SEP KB

http://www.symantec.com/business/support/index?page=productlanding&key=54619

Blocking a Website using Symantec Endpoint Protection

Article URL http://www.symantec.com/docs/TECH92405