Welcome to the site! Your "Wantlist" can be populated by adding individual cards or sets.
Using the Random Card of the Day as an example, if you navigate to the page for this individual card, you can scroll down to the "Collection" and click on the arrow next to the name and select "Add to Wantlist".
https://www.tcdb.com/ViewCard.cfm/sid/362213/cid/21336132/1973-Dutch-Gum-Serie-P-(Holland)-33-Wings
Additionally, if you wanted to add the whole (or certain cards) from which that card is from to your Wantlist you can navigate to the set
https://www.tcdb.com/ViewSet.cfm/sid/362213/1973-Dutch-Gum-Serie-P-(Holland)
click "Update Your Collection" on the right side of the screen
https://www.tcdb.com/ViewCollection.cfm/sid/362213
Then "Choose an Action" and select an option such as "Add all missing cards to Wantlist" or individually select cards
https://www.tcdb.com/ViewCollection.cfm/sid/362213
You can also do the same for all cards associated with a profile, such as
https://www.tcdb.com/Person.cfm/pid/339517/Wings
You can go to Collection Summary and click Add/Update Wantlist
https://www.tcdb.com/CollectionSummaryP.cfm/pid/339517
Many questions you may have about the site can also likely be answered by the FAQs; specifically the "Tracking Your Collection" portion for Collection, Wantlist, and For Sale / Trade.
https://www.tcdb.com/FAQ.cfm
