Penalties will decide the match if the score is level at the end of 90 minutes on Tuesday July 21.
Tickets are on sale at £12 for adults, £7 for senior citizens, and £4 for under 16s.
Season-ticket holders can purchase tickets at the discounted prices of £10 adults, £5 senior citizens and £2 for under 16s.
Both games are free for under-sevens
Fans can contact the Sixfields box office in person, by email at box.office@ntfc.tv or by calling 01604 683777