The selling point of this electronic dictionary is how easy it is to carry around.
Literal
This electronic-dictionary [topic-は] portable-easy place [subj-が] key-point [copula-です].
味噌 literally 'miso paste' is used figuratively to mean 'the key selling point / the thing to brag about' — as in 手前味噌 'blowing one's own horn.' 携帯しやすい uses the ~やすい suffix on 携帯する 'to carry,' and ところ 'the aspect/part where' nominalizes the whole quality.