Well here you will be taught how to create scanlines using Photoshop. This is one of the most basics effects to do so you shouldn't have any trouble.
1. Click File > New and use these settings. Make sure its on pixels. Later once you need different width scan lines you can change the height to accomidate that.
2. Next with the color that you want your scan lines to be, usually black. Fill in the first 2 rows, using the pencil too. Then click Select > All.
3. Now go to Edit > Define Pattern. This will set this as the pattern.
4. Now click the image that you want to put scan line on. Click Edit > Fill. A box will pop up. Make sure it set to pattern not foreground color. Then just hit ok.
