7. Add borders
There are several ways to complete the effect with a retro border. To add a Polaroid-style border, grab the Rounded Rectangle tool and set the Radius to about 40px in the Options bar, then drag a rectangle over your image to add a shape layer.
Cmd/Ctrl+click the shape layer’s vector mask thumbnail in the Layers Panel to load a selection of the shape then go to Select>Inverse.
Next, hide the shape layer and create a new layer. Go to Edit>Fill and choose Use: White or select any colour that you like.
You can use the Stroke command to add a simple black border. Make a new layer then press Cmd/Ctrl+A to select all. Go to Edit>Stroke and set a width such as 50px.
Choose a border colour then set Location: Inside and hit OK. For rough edges, click the Add Layer Mask icon then grab the Brush tool and choose a rough brush from the Brush Preset picker.
Load in brush sets by clicking the icon at the top right of the picker. Wet Media Brushes work well.
Paint with black around the edges to rough up the border, varying brush tip size and brush Opacity as you go.