"The robber beat my back with a mace."
Translation:DubwIj moqmeH ghanjaq lo' HejwI'.
In addition to what mizinamo says, also understand that there is no specific formula for translating with. In addition to the purpose clause this example uses, I could also say DubwIj moq HejwI'; ghanjaq lo' The robber beats my back; he/she uses a mace or DubwIj moqDI' HejwI', ghanjaq lo' When the robber beats my back, he/she uses a mace, or any other such variation you can think of. You don't even need to use lo'; you might say something like DubwIj moqmeH HejwI', ghanjaq Qach In order to beat my back, the robber wields a mace. Whatever gets the concept across is fine.
Just forget about a word-for-word translation of with. There isn't one.
So, there is no direct way to say "with something"?
Klingon doesn't have any prepositions; the closest equivalent are type-5 (syntactic) noun suffixes, and there is none (that we have learned yet) that means "with".
We have "in/at/on" (-Daq), "from" (-vo'), "for/to" (-vaD), "because of" (-mo') but not "with" or "without" or "thanks to" or "despite", for example.
Do we have to always turn the phrase around like this: "I eat my food with a fork" becames "SojwIj vISopmeH, puq chonnaQ vIlo'"?
That's how I would express it, yes. Literally, "In order to eat my food, I use a fork."
And for the other meaning of "with" ("in the company of, together with"), you may end up using tlhej, e.g. vaS'a' vIjaH. mutlhej mara. "I went to the Great Hall. Mara accompanied me." = I went to the Great Hall with Mara.