Subscribing to individual articles within a publication
The stored procedure sp_addsubscription allows for you to specify that you want all articles (i.e. tables) or just one.  If you want a subset of articles in a publication, you just need to run the sp_addsubscription once for each article that you want.  It looks like the sp_addsubscription defaults to @article = 'all'
My suggestion is to go through the New Subscription Wizard and have it generate the script only.  Then you can go in and modify the script as you need it.  You would need to add multiple sp_addsubscription lines.