"I put the pickles on a small plate."
Translation:J'ai mis les cornichons dans une petite assiette.
What you say makes sense. It all depends on context.
"I put" is both the present and the simple past tense (for an action that took place at a definite time in the past).
We do not know the context, but it could be...
"I put the pickles on a small plate this morning." You can omit the "this morning" and it can still be understood as being in the past if you are not doing it then and there.
For the present tense, the context could be... "Look at how I am doing this. I put the pickles on a small plate." Said whilst putting them on the plate. Maybe this usage comes up less often (unless you teach cookery).