Usually the method depends on what you want to do with the texture later.
If you want to get the whole rendered scene back to matrix(for recording mostly), you can use jit.gl.asyncread.
If you want to do some kind of post-processing first and then display it later, you could render your 'scene' through jit.gl.sketch with @capture attribute set to name of destination texture.
All the objects rendered through that sketch should then be @automatic 0.
Even if you have a bunch of sketches that make up your scene, you can still set their @automatic 0, give them @name and render them with a 'master' sketch.
Try searching the forum and especially Andrew Bensons recipes - this is quite a recurring subject.