Your investment philosophy should describe what type of portfolio you're constructing (e.g., mid-cap blend fund), whereas your process should explain how you're picking your portfolio's holdings (e.g., stock screener, subset of an index, companies you like or sell products that you've used, etc.).

As for the benchmark, you can either use an index or an appropriate index mutual fund or ETF. For example, if your portfolio is a mid-cap blend fund, you can use the S&P Midcap 400 index or the Vanguard Mid-Cap Index Fund (VIMAX) or the Vanguard Mid-Cap ETF (VO), or a similar mutual fund/ETF from any other fund family.