IPA: /ɪnˈtɪəriəli/
KK: /ɪnˈtɪr.i.ɚ.li/
In a way that relates to the inside or inner part of something.
The room was decorated interiorly with beautiful paintings and soft lighting.
Interiorly → It is formed from "interior" (from Latin "interior", meaning inner or within) and the suffix "-ly" (meaning in a manner of). The word "interiorly" means in a manner that pertains to the inner part or inside.
Think of 'interior' meaning 'inner' — and '-ly' indicates a manner. So, when something is described as interiorly, it refers to how it relates to the inner aspects.