Tariffs end up being a zero sum game.
We charge them more, their businesses charge customers more, we are buying from them(hence the trade), so we end up paying the difference.
In retaliation, they charge us more, our businesses charge customers more, they are buying from us(hence the trade), so they end up paying the difference.
So, how are tariffs effectual?
The institution of them, and the ensuing trade war that follows, will strain all parties. As Trump is fully aware, in negotiation, "something's gotta give". He expects that we can sustain a trade war far longer than the Chinese, since they've been blowing all their money on military for the last 10-12 years. The end result? The "Red Dragon" cowers back down and accepts the reality of the situation, that *WE* know he can only blow smoke.
At that point, and with their economy holding on by a thread, they will return to the table. Then what happens? Appropriate agreements are reached, and likely more in favor toward the US since China won't have a leg to stand on anymore. Both economies see a BOOM over the next few decades where we become stronger partners and, dare I say it, allies.
The communist Chinese are not too familiar with the concept of helping up one's "enemy". The US is all too familiar with it.
You can't name a nation in our history that we didn't pour money into after blowing it away. This has resulted in strong allies and amenable relationships.
China will be next. They will feel the squeeze without a shot being fired. They will crack. Then, we will pick them up and lift them to a higher place than they've ever known.
With Eastern cultures, if they are unwilling to see you as an equal, even if an enemy, then you must break them until they fully realize it. It doesn't always take force(Hiroshima and Nagasaki), and we'd like to avoid that at all costs. Tariffs seem like a perfectly reasonable alternative.