You need a GSM phone that operates on the North American bands, 850/1900 MHz. Obviously SpeakOut phones fill that bill. So do unlocked GSM phones. Because SO uses the Rogers network, phones that are locked to Rogers, including prepaid and postpaid phones, will work as well.
A SIM is a small chip that fits inside a GSM phone. It identifies "you" to the carrier, i.e. your phone number and with prepaid, your airtime credit. SIMs are designed to be easily moved from one phone to another but each SIM works only with the carrier who issued it. So, for example, you can't make a Rogers SIM work on SO.
The easiest way to get going on SO is to buy a phone (which includes a SIM) from 7-11. But if you don't like their phones you will need to get a phone separately plus a SO SIM. One way to get a SO SIM is to buy one from a seller on this forum.
Another is to go for the current buy $100 airtime, get free phone promo, then:
1. keep the SIM and airtime
2. sell that phone privately
3. buy the GSM phone you really want and insert the SO SIM into it
> How do I swap a SIM card?
On most phones, just pull out the battery to reveal the SIM underneath. Then slide out the SIM or open a clip to release the SIM and replace it with the new SIM. The instruction manual for your phone will have a detailed description of how to do this.