[Ethereum] How to actually setPrices of the token

There are actually a few things you have to take care of:

1. Make sure that there are some tokens at the token contract address. If there is not any, then noone is able to buy tokens, since every purchase is made not from the owner of the token but from the token contract address (this).

   If you have a look at the source code you linked you can see the line Transfer(this, msg.sender, amount) in the buy function. This means that the contract tries to send tokens from its own balance, but at the creation of the token contract, only the owner of the token contract possess tokens, not the contract itself. So just send some tokens from the owner of the contract to the token contract itself!

2. Did you set buyPrice and sellPrice? If you did not, then they are 0, and division by zero will give you an exception at the buy().

Distinguish between price and rate. Call rate the value inside your smart contact. The rate should not be adjustable. By making it non-adjustable, anyone who is interested in your ICO knows what they are getting before buying. They don't have to trust anyone or anything. They "see" the exact exchange rate in the code. Because the code is immutable (and the purveyor of the software does not have the ability to change the rate), the ICO participant is able to trust that they will get exactly what they are expecting.

I think of price as what the token trades at relative to other currencies off-chain. The price is also out of the token purveyor's control. People buying and selling tokens determine the price through simple market forces and supply/demand.

Note: I said above that exchange rate should be not adjustable. To anyone reading this--never buy into a smart contract with an adjustable rate. I don't mean a rate that changes over time--I mean a rate that the owner of the contract can change at will. They could start the ICO, wait a few seconds until the FOMO picks up, change the rate, and take tons more money than people expect in exchange for tons fewer tokens.

Note 2: I'm not sure exchange rate is the right word. If someone suggests a better word, I'll change it.

Note 3: I would definitely not buy into this ICO given the OP's obvious lack of understanding of what he/she is doing. That's me speaking personally, not intended in any way as advice.