A lesson on Memrise.com has the word "puesto" defined as an adjective meaning "placed, set". I've not found any examples that use "puesto" according to this definition.
May someone give an example sentence on how to use "puesto" as an adjective?
Puesto is a participle, so it is a non-finite form of a verb. A couple of examples would be when you refer to a set table (una mesa puesta para dos personas, a table set for two), or the popular Spanish saying "a rey muerto, rey puesto", said when someone leaves a post and is quickly replaced, which would be roughly and literally translated as "when a king dies, another is put in his place".
On its entry for "puesto/a" RAE states three different meanings of puesto
as an adjetive:
adj. Resuelto, empeñado, determinado. Puesto en librar a la señora.
adj. Bien vestido, ataviado o arreglado.
adj. coloq. Experto o buen conocedor de la materia o asunto que se expresa. Muy puesto en matemáticas.
On italics are the examples RAE provides. An example for entry number two:
Los invitados han ido muy puestos a la boda.
In Spain puesto
is also used to define someone who is high on drugs.
Juan está puesto, se nota que hoy se ha drogado.
Juan is high, it's clear he has taken some drugs today.
But I guess this is kind of a slang, I don't know if it's used outside Spain.
The word "puesto" is most used as a verb. As you said used similar as placed or set like:
"He puesto la pelota encima de la mesa" --> I put the ball on the table
"Puesto" as adjective is more colloquial, has many uses, for example:
"Estás muy puesto en tu trabajo" --> You are very concentrated in your job