But Peter followed Him from a distance [as they were going] to the courtyard of the head priest. He went inside [i.e., eventually. See John 18:15-16] and sat down with the [Jewish] officers to see how things would turn out [i.e., with Jesus' trial].

Even

Simon Peter followed along with another disciple. [Note: Some think this refers to the apostle John himself, but there is no strong evidence in favor of that conclusion]. Now that disciple was [well-] known to the head priest, so was able to enter his courtyard with Jesus

And he

And when they [i.e., the priest's servants] had built a fire in the middle of the courtyard, they sat down together [i.e., to warm themselves. See Mark 14:67], with Peter [sitting] among the group.

Now the [head priest's] slaves and the [Temple] guards were standing around a charcoal fire they had made to warm themselves by, because it was cold. And Peter was also warming himself with them.

And warmed

And He became anguished as He prayed more fervently; even His sweat was like drops of blood falling to the ground.

General references

And those who had arrested Jesus led Him away to the house of Caiaphas, the head priest, where the experts in the law of Moses and the [Jewish] elders were gathered.