Schopenhauer was inspired by Indian philosophy. He auto-didactively learned Sanscrit to read original texts (Vedas).
One idea of it is that the circle of life has to be broken to get to Nirvana. The Will to Live therefore is something bad as it prevents us from getting there.
The solution is NOT suicide in the sense we know. It is rejecting the Will to Live. It is not drinking, not eating, but these should be just forms of not willing anymore (usually by meditation), because in the moment we are willing anything at all, we would automatically serve the Will to Live as living creatures. Real suicide would not be overcoming the Will to Live, it would be fighting it (therefore acknowledging its evidence) and it is a fight one cannot win (rebirth).
Living is willing (following desires, bodily needs etc.), willing is living
Therefore instead of saying we must "break" the circle of life (which is probably as impossible as fighting, ending, etc. it) it could be better to say we must transcend it. It cannot be overcome from within, you have to get over it (in this very sense of the picture of transcendence).
In this sense, living is suffering from the Will to Live. We cannot influence this, it is an external fact and therefore we are "just suffering". As long as we are living, we ipso facto cannot evade this. We have to stop living, becoming sheer (and immortal) being, not end it, since a circle has no end. The idea of living as suffering is a picture he liked about Kant's epistomology.
It is described in "Die Welt als Wille und Vorstellung" (The World as Will and Representation).
As a sidenote: Although this is in fact his ethical conception, he obviously never lived after that and did not take it too serious. He actually fled from the cholera in Berlin in 1831 showing his own strong will to live whilst Hegel stayed there and died from it.
Most of this can be verified on Wikipedia.