First option is with Solo Ads. One off ads that are placed on a pre existing list that, if clicked, send visitors to your website. For this you first have to create a banner ad or become an affiliate for another product and use theirs if they have one. Then look for a list owner, you can do this by searching for solo ads on line. Find a good one that matches well with your site and then contact them with your idea.
Next they agree to put your ad on their site/list and then you agree a price on how many clicks you want to receive or how long you want to advertise for.
Pay and wait for visitors.
Banner ads are usually placed on your own site to promote other products. They can also be placed on other sites for a fee. Examples would be Google and Bing and Facebook. You can place adverts on these easily, just visit their main pages and look into their prices and options – be sure you target the correct audience for your ads to ensure value for money.
Pay Per Click ads are what they say they are. You find a vendor and then pay them to host an advert for you and how many clicks you want to have to your site before the advert is removed.