not entirely true. your pc onboard sound or soundcard is essentially a dac+amp since it converts from digital to analog. but yes, i get what you mean (you never used an external dac).
in the case of the fiio e10k, i'd likely use the line-out (unpowered) jack on the rear since your speakers are self powered and connect it to the rca inputs on the speakers. the powered front connector i'd use with headphones. besides an adapter cable theres not much else to say.
now, technically theres another option i did not list since which would be usb audio interfaces. those act as a dac as well though arent generally going to have strong amps, some may be okay with some headphone without one while others absolutely need an amp before headphones. ones like the scarlett 2i4 (though there may be cheaper options with the feature) have balanced outputs for going to your speakers. generally audio interfaces are used by people who record and use XLR style microphones. think youtubers, twitch streamers, etcetera.
not sure what exact purposes you have or your future plans. just thought i'd fill in the missing piece. a usb dac+amp like the fiio e10k is more for casual listening and not for people who record professionally.