Basically, the main perk of free trade is its low prices, since firms go to nations with the losers a costs of production, they then can charge lower prices for the final goods. This then frees up the money in the consumers pockets which can be A) spent and sent to a business which will then purchase productive factors which will continue to send the money around the economy, or B) it will be saved and sent to the capital structure where it can be loaned out and benefit the economy that way. However, it isn't just consumer goods! Land and capital factors of production are then cheaper, meaning that DOMESTIC production is then cheaper, meaning the capital funds for productive factors expands and more labor can be hired among other production factors. Long run, there is 0 correlation with free trade and unemployment, and protectionism has caused unemployment as well by upping factor costs.