Using the "net help share" command you will see that the syntax is as follows:
net share sharename=drive:path
For example, if I had a folder S:\Public which I wanted to share as "Public" the command would be:
net share Public=s:\Public
The above command will automatically grant "Everyone" with Read permissions only. If you want to grant Everyone with Full Control the command would be:
net share Public=s:\Public /GRANT:Everyone,FULL
Keep in mind that NTFS permissions still apply, so even though you might have granted EVERYONE with FULL access to the share, you'll still have to check the NTFS security permissions to ensure that the right people have permission there too.