Hello and welcome! We are glad you here, and we hope you will join in the fun here as we talk about Get Backers.
As Lovux the Great says, access to the Releases section of the forum will be automatic for you once you have reached the proper number of posts in the forum -- which happens to be 15 posts. When you have posted 15 times -- in any thread on any topic -- you'll be able not only see the Releases thread, but you'll be able to download the chapters that have been shared up to that point and any future chapters.
It takes hardly any time at all to reach 15 posts, and in the process we will get to know you better, and you us, so post away and enjoy yourself, and before you know it, you'll be reading the new chapters.