You can easily get to trade LTC/USDT pair on exchanges like bittrex, binance or poloniex, without having to register on the tether platform, which I believe should make things easy for you. Here is a step to guide you.

- Open an account on https://bittrex.com or https://binance.com
- Familiarize yourself with the exchange
- Deposit your LTC on any of the exchange address
- Then, you can search for the LTC/USDT pair and there you have it.

However, as a complete noob who wants to trade, I really hope you know what you are doing.