Once you've got their attention and created some interest, it's time to ramp things up. This is where you build desire. You build desire by drawing attention to things that are problems for your target audience. For instance, they may want to lose weight, gain muscle, save money on a home purchase, or become a better public speaker.
By using your marketing to evoke positive emotions of what they can achieve with your product or service, their desire levels will increase. In addition, don't be afraid to point out the negatives. Remind them how awful it is to be overweight, bored, a poor speaker, ripped off, and all the other consequences that come along with not choosing your product or service. This sets you up to be able to close the deal.
Keep in mind that desire is not created through facts and literature. You need to evoke emotions. Images and audio assets are great parts of your digital marketing arsenal to use here. Anything that helps your customers envision their lives with your product (or without it) will solidify the desire they have to make a change in their lives. Use every angle you can think of in making your product seem attractive: appearance, efficiency, safety, cost, social standing, etc.