How to add glowing lines effect

Final image

 


















This will be a very quick and short tutorial
Open you Image in Photoshop

Firstly, create a new layer, then grab your Pen Tool (P) and draw out a path line as per below

 

Now, Select the Brush Tool (B) and set your diameter to 7px, with the Opacity and Flow at 100%, and foreground set to your desired color. With your path still active, go back to the Pen Tool, right click on the canvas, and choose "Stroke Path." 

Note: If you wish to make the line at the beginning and the end of your stroke thinner then check the box "Simulate Pressure" and press OK.









Note: The line will be colored depending on the color you set on the foreground

As per below , the line will be colored but then we need to delete the path
Simply right click and select delete path

The path will be deleted and your line will be more clear

Now we need to create multi- colored lines 
Choose a brush tool and start painting on your line as per below, it doesn't have to be perfect we will modify it later. To change color of your brush simply click on foreground tool then select desired color then paint on the line.

Hold ALT, then point your mouse in between the two layer (containing the multicolored line and the one with just one color) a when a small box with an arrow pointing down appears then click this will transform the line as per below

 

Play with color so as to add more light to the line
Image - Adjustments - Brightness/contrast  

 
Now we need to delete the parts you want hidden behind the body,With your stroke layer selected choose eraser tool and start erasing areas you want to appear as if they are behind the body