How do I create this lens flare/warm glow?

My guess is that is not an effect, but is a real lens flare from shooting with a strong back light.

To simulate it, and another way would be to use a custom gradient.

Warp the gradient (I tried using a radial gradient but could not get it to the right shape)

Blur the gradient layer to soften the outline. but note a lot of the gradient is out of frame so the left edge is not blured.

In case you don't know, you can reduce the opacity of one end of the gradient as below.

To finish the effect I added a layer with blend mode set to Color and with opacity reduced way down to 10%

You could do the same thing with a Hue/Sat layer with Colorize checked.

It's hard to say how it was done on your example, but you could try this:

With the original photo on the bottom layer, I added a Color Fill layer with red, set the layer to Multiply blend mode, lowered the opacity to 67%, and lightened the red on the backgroiund using a layer mask.

Then I added a Gradient Fill layer with a yellow/orange Radial gradient, added a layer mask, made an  elliptical selection in the mask, filled with black outside the selection, set the layer opacity to 80%. 

Experiment with the layer blend modes and amount of layer opacity, and the areas you want to mask.