That is a very opened ended question...
I suggest using the search engine and/or google using the term "central filtration" on google you might need to add in "aquarium", "fish" or "fish tank"...
It is possible, people do it all the time... I've done it... but there are a ton of little details and it would take a ton of typing to cover even most of those details...
A couple questions... are your 10 & 20 gal tanks drilled? Have you used a sump before?