Microsoft Forms is still in preview for commercial (business ) tenants and is available with:
"all commercial customers can access Microsoft Forms through the Forms tile in the Office 365 app launcher or directly at http://forms.office.com"
There's no announcement yet how long the preview will last but keep an eye on the blog:
"We are working proactively toward removing preview label. It will happen sometime after Microsoft Ignite conference. Will keep you posted"
Office 365 commercial customers can access Microsoft Forms via Office 365 app launcher