How to modify Perlin (not simplex) noise to create continental like terrain generation
Perlin noise is just a base block, not very interesting by itself. You don't need to modify it, but to combine and filter it in interesting ways. Look at how to make fractal Brownian motion (fBm) with it for example, which combines octaves based on few parameters to get a richer texture.

The question of terrain rendering is a difficult one and a topic of active research. Many generated terrains have this artificial and uninteresting look. This is exactly what the paper "Modeling Real-World Terrain with Exponentially Distributed Noise" tries to address, by proposing a formula based on statistics measured from actual terrain, which yields more convincing shapes.

Another source of valuable information is Iñigo Quilez's website, where he mentions procedural generation a lot, including tricks to fake erosion.