First off you should be well aware that by Mining STEEM you are actually earning STEEM POWER and not STEEM tokens, so mining can be used as a means to increase your influence and earnings when interacting further on the steemit.com website and not as a means for getting crypto tokens that you can quickly turn to cash...
If you don't know how to get started mining for STEEM, then you can find an easy Mining guide for Windows here that should get you started in no time.
The big question however is How Much Can You Earn By Mining STEEM? The answer unfortunately is not straightforward as you may think it is, because there are multiple factors that can influence your earnings:
The mining hashrate you get with your processor, the number in hashes per second (HPS) is being displayed in the miner window when you are mining and after that you can see an estimated time in minutes for how long it may take you to find a block with that hashrate.
With mining Luck is always a key factor that influences how much you mine over a given period of time for better or for worse.
The current number of miners competing with you for finding a block and the overall hashrate of the network also influence the outcome.
So how about some numbers now based on real world experience from mining STEEM for a couple of days now...
With a high-end CPU such as an Intel Core i7 processor with four cores you can expect to get something like 30-40 thousand hashes per second (30-40 KHS). Do note however that the maximum hashrate is achieved only when you fully utilize the CPU with a number of threads used for mining that is equal to the number of cores (logical and not physical). If you do not fully load the processor you will be getting lower hashrate and it will take more time for successfully mining a block.
With about 33 KHS worth of hashrate you can expect to get between 1 and 3 blocks per day if you are mining STEEM 24/7, the results can be influences by the factors explained above. This essentially means that you will be earning between 1 and 3 STEEM POWER per day with a similar setup, so not a bad way to increase your influence on the steemit.com website on a daily basis without too much effort by just leaving your computer mining for STEEM.
And if you have lets say just 1/3 of that hashing power or about 10000 HPS, then you can expect to also be able to earn just about one third of the rewards or 0 to 1 STEEM POWER per day etc.
For the Step by Step Guide on Getting Started Mining Steem on Windows