When a visitor is on (or returns to) your website, you want to remind them of the items that they have previously viewed. There is a good chance at least one of these items is still relevant to him or her.
To do this, you can create embedded content on your website. If you are unclear as to how this works, please check out this link
Generally people will place their recently viewed items on their homepage. This allows the visitor to immediately see these items the moment they open up your website (if they have visited items before). These steps will tell you exactly what you need to do to create this specific touchpoint.
Create a touchpoint for website - embedded content
Select your choice of content (all content is generally fine here, but it is recommended to filter on product and maybe even only the ones in stock) and select the recommendation strategy last viewed or last viewed & most relevant.
Select the CSS path you want to use and set the occurrence to "first".
Make sure the audience targeting is set to "is on homepage / equal / yes".