Well, start like this, on form load or other event get all the files in given dir:
string[] filePaths = Directory.GetFiles(@"c:\MyDir\", "*.bmp");
set the first item of the array in the picture box and the current item index in the page.
int currentItem = 0;
int maxItems;
...
maxItems = filePaths.Length;
then set the image in picture box
Image image = Image.FromFile(filePaths[maxItems]);
pictureBox1.Image = image;
pictureBox1.Height = image.Height;
pictureBox1.Width = image.Width;
Set the next image on every click:
Image image = Image.FromFile(filePaths[maxItems]);
pictureBox1.Image = image;
pictureBox1.Height = image.Height;
pictureBox1.Width = image.Width;
maxItems++;
This is a rough explanation, it is on you to experiment a bit.
Cheers