How can I learn how to form the corresponding participles such as hidden, fallen, laden, etc

Question

I acknowledge that sometimes there is a different way to say things in Russian, but I've seen the following, and do not know where to begin to know how it is derived:

"У неё было спрятано шесть ананасов."

Just seems to be no information out there on participles. I found info on forming active present and past participles here.

But it doesn't really help in the instance of participles ending in -en.

Answer 1

The participles ending in -en usually, but not always, correspond to the passive voice. That's why you don't see them on that page; it's about active participles. Passive participles are discussed here. I will expand a bit on the material outlined there.

The Russian term for passive participle is страдательное причастие. There's no form that is common to them all. Many such word will have -анн- or -енн-:

hidden, long form: спрятанный, спрятанная, спрятанное, спрятанные
hidden, short form: спрятан, спрятана, спрятано, спрятаны
frozen: замороженный (make all the other forms yourself)
laden: нагруженный

Often an -en participle can be translated with an adjective as well:

laden гружёный
frozen мороженый

Unlike страдательное причастие, these are written with a single -н- in the long form. An easy rule to remember, isn't it?

In fact it's hard even for native speakers, because the distinction between these two parts of speech is somewhat artificial.

Other examples:

stolen: краденый и украденный
written: писаный и написанный

But often there is no -анн- or -енн-, there's -т-:

hidden, long form: скрытый, скрытая, скрытое, скрытые
hidden, short form: скрыт, скрыта, скрыто, скрыты

Other examples:

beaten битый
taken взятый
broken разбитый (also сломанный, ломаный)

Sometimes an English -en participle corresponds to a Russian active participle (причастие действительного залога).

fallen павший (or падший, depending on whether it's a warrior or an angel)
rotten сгнивший (there's an adjective too: гнилой)

The short form of the active participle is rarely used, if ever.

Note that страдательное причастие can be used in the present tense too (mostly in writing). Such forms have -ем- -им- or -ом- in them:

(being) driven ведомый
(being) thrown бросаемый
(being) blown раздуваемый