Most of the terms are spelled out in the
Terms & Conditions that you agreed to during the application process. Quoted below. It can take as long as three months from the date of your app (or longer if you don't make a purchase within the first month). Note also that the base fare on the first ticket must be at least $250. The advance purchase requirement is 14 days, and the blackout dates are listed
here. The certificate only applies to roundtrips within the lower 48 and to Canada.
You cannot make a reservation before you receive the certificate for several reasons. The certificate has a code on it that you need to provide when making the reservation. Your code is only valid for reservations made within a certain length of time (a few months after receiving the certificate). You won't know the code until you get the physical certificate. You are also instructed to mail the certificate within 24 hours of making the reservation or risk cancelation of the reservation.
Companion Certificate: For the $89 Annual Fee MasterCard, the Primary Cardmember is eligible to receive one companion certificate valid for two $99 companion tickets each year. For the $49 Annual Fee MasterCard, the Primary Cardmember is eligible to receive one $149 companion ticket each year. Your first certificate will be sent to you 6 to 8 weeks after the Account has been used for at least one purchase and your Annual Fee has been paid. Each year thereafter, you will receive your companion certificate 6 to 8 weeks after your account opening anniversary and after the annual fee has been paid. The companion certificate is valid for round-trip coach class travel within and between the contiguous U.S. and Canada when the Primary Cardmember purchases a qualifying ticket (minimum fare purchase of $250 required). Additional taxes, fees and charges including (PFCs), Federal Excise Taxes, Canadian VAT/GST and customs/immigration charges as well as the September 11 Security Fee apply to all tickets purchased and are not included in the base fare. Other companion certificates restrictions apply including advance purchase requirements and black-out dates and will be provided on the actual certificate.