The most common place to sell tokens is on an exchange. Exchanges are decentralised (collectively referred to as DEX), or centralised. Getting your token listed on a centralised exchange is a difficult and expensive process. Most centralised exchanges will not list a new token unless it has high liquidity (lots of people already hold and/or use it), is well-known or otherwise has a high profile, and may require a substantial fee for listing the token.
On the other hand, access to decentralised exchanges is quite easy. Because they are decentralised, anyone can list a token. The methods for each exchange differ for each case, so it's worth investigating more than one DEX before choosing how and where to list your tokens. You ordinarily place a sell order on the exchange for some of your tokens, and if there is sufficient demand, buyers can choose to place a buy order (usually paying in ETH).
The price you set for your token is up to you - in the case of a token that you have created, you can choose the price that you want to sell for. Potential buyers can then decide if they feel the price is a fair one.