“What should be done for his disciples out of compassion by a teacher who seeks their welfare and has compassion for them, that I have done for you, bhikkhus. There are these roots of trees, these empty huts. Meditate, bhikkhus, do not delay or else you will regret it later. This is our instruction to you.” - MN 19
He turns his mind away from those phenomena, and having done so, inclines his mind to the property of deathlessness: 'This is peace, this is exquisite — the resolution of all fabrications; the relinquishment of all acquisitions; the ending of craving; dispassion; cessation; Unbinding.' (Jhana Sutta - Thanissaro Bhikkhu translation)
In terms of practicing, Sharon Salzberg's Loving-kindness is very accessible. She lays out the instructions pretty simply and clearly. I liked Alan Wallace's The Four Immeasurables for a further discussion of them.