Yes, absolutely, you have a few different ways to do this.
If you want to enter a coin manually, you can click on Enter Coins on the top menu and then click New in the top left above the table. You can then enter the Buy and Sell amounts/currencies, along with any fees or comments you want to add.
There are also options to import exchange data or you can add API data from your ETH/BTC/Altcoin wallets, to track your transactions. It is good to make a plan about how you will track your trades. In my main CoinTracking account, I track every transaction from fiat to crypto, between all cryptos, and then back to fiat. That way you have a complete record for things like tax calculations.
COSS.io does not have this automatic functionality built in right now, as they are still in beta, but you can import your COSS trade data in a similar way that the allocation data was input. Try copying the trade history data into Excel and then adjust the column associations on the Custom Exchange page until they make sense. :)
There is a lot of additional information about these functions here on the CoinTracking site: Support > Contact & FAQ and Documentation.