I'd like to use some beautiful patchs (like a loopsample player, a grain synth etc.) inside a patch create by myself to manipulate them in other ways... but I find lots of problems trying this. I suppose I'm a bit confused about the place where pd store my new patch, how pd search for libraries and how it use them, if I need to copy the file of the external patch I'd like to use (e.g. the sample loop of the examples manuals) inside a specific directory or if it's possible just to copy and paste it inside the new patch... Do I add inlets and outlets at that external patch and use it like an abstraction??... I'm really very confused, but I try again and again... thanks in advance for the help and sorry for my English

You are correct!

copy and paste it into your existing patch or put the .pd file into the same directory as the patch you are working on and you use it as an abstraction by typing [name_of_abstraction] (without the .pd!)