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-crud-operations-with-permissions

CreatePermissionForUser.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Telerik.Sitefinity.Modules.Blogs;
using Telerik.Sitefinity.Security;
using Telerik.Sitefinity.Security.Model;

namespace Telerik.Sitefinity.Documentation.CodeSnippets.DeepDive.Security.Permissions.ManagingPermissions
{
    public partial class PermissionsApiSnippets
    {
        public static void CreatePermissionForUser(string userName)
        {
            UserManager usersManager = UserManager.GetManager();
            BlogsManager blogsManager = BlogsManager.GetManager();

            Permission permission = blogsManager.CreatePermission(
                BlogsPermissions.Sets.Blog.SetName,
                blogsManager.GetSecurityRoot(false).Id,
                usersManager.GetUser(userName).Id
            );

            blogsManager.GetSecurityRoot(false).Permissions.Add(permission);
            blogsManager.SaveChanges();
        }
    }
}