SF_10.1, SF_10.2, SF_11.0, SF_11.1, SF_11.2, SF_12.0, SF_12.1, SF_12.2, SF_13.0, SF_13.1, SF_13.2, SF_13.3, SF_14.0, SF_14.1, SF_14.2, SF_14.3 - https://docs.sitefinity.com/for-developers-create-forum-groups

CreateForumGroups_CreateForumGroup.cs

using Telerik.Sitefinity.Forums;
using Telerik.Sitefinity.Forums.Model;

namespace SitefinityWebApp
{
    public class CreateForumGroups_CreateForumGroup
    {
        public void CreateForumGroup(string groupTitle, string groupDescription)
        {
            ForumsManager forumsManager = ForumsManager.GetManager();

            ForumGroup group = forumsManager.CreateGroup();

            group.Title = groupTitle;
            group.Description = groupDescription;

            forumsManager.SaveChanges();
        }
    }
}