The only way to get more engines than supplied by your engine supplier is to purchase them with tokens. Go to cars > repair > buy parts and engines (the + sign over a green button next to your parts and engines counter). If you somehow can't find it, here's the link: https://igpmanager.com/app/d=parts
2 car teams get 20 engines per restock. 1 car teams get 10 (Lee is in a 1 car league).