Welcome. What are your intentions with the pair of macaws? To have them become pets or to continue to be breeder birds? If the latter, do you have experience hand raising parrots? In any case, the best "method" to earning a distrusting birds trust is to first get them used to you (this could take weeks or even months) and then to start training them at their pace (again, a venture that could take weeks or months more to get them stepping up consistently). Usually it is suggested you start with reading and/or just talking out loud to them every day. This helps them become used to you as a calm, non-threatening presence. It doesn't matter what you read or say to them, it's all about tone of voice. Use a calm, soothing tone of voice and if they voluntarily approach you in their cage, have treats ready. You can also snack on something healthy yourself, like grapes or carrot sticks and when they become interested in what you're eating, share with them. It's a positive they already accept treats from you, but from a pair of breeder birds, I'd expect months more before you're at a point to begin training stepping up and other basic training activities. It would also not be unusual if one takes to you more than the other.
After the appropriate quarantine period (generally accepted as 6 weeks for new birds) and an exam by an avian vet to ensure they are healthy and free from disease, there is no reason they cannot be in the same room with your finches, though for obvious reasons they should be housed separately in their own very large cage and not allowed to interact with the smaller birds.