DLsite sells authorized English translations, but translating the storefront does not translate everything you buy. The interface language, product description and actual work are three separate things to check.
You can be reading a perfectly understandable description of a book whose dialogue is entirely Japanese. The useful question is: which edition will appear in your library after checkout?
Match the edition, not just the cover
Start with the creator's own announcement or the work you already know. Compare the title, creator or circle name, language description and sample on the translated edition. When two listings use the same artwork, save their product IDs so you can tell them apart later.
The sample earns its place here. For a comic, inspect actual dialogue pages. For a visual novel, look for the languages supported by that game edition and try its demo if one is provided. An English title, sales paragraph or review is weaker evidence than English text inside the work.
Useful Japanese words include 英語版 (English edition), 日本語版 (Japanese edition), 翻訳 (translation) and 字幕 (subtitles). Translate the surrounding sentence too: “English translation planned” is a different promise from “English edition included.”
Before paying, you should be able to finish this sentence: “I am buying this creator's work in English, in this format, for this device.” If one part is blank, go back to that part of the listing.
What “Translators Unite” means
DLsite's みんなで翻訳, known in English as Translators Unite, provides a route for translations authorized by creators. Eisys, DLsite's operator, describes the arrangement in its translation-program announcement: creators grant permission and translators produce editions for sale. Its language announcement explains that proceeds are shared with the original creator and translator.
That makes an authorized translation a way to support the work's creator. It does not mean every title has an English version, that every edition has the same translator, or that buying the Japanese original automatically includes a later translation. Check the edition you are purchasing.
A translator credit also gives you something useful to follow. If a sample reads well and you like the choice of works, look for that credit again rather than starting from a random English-language search result each time.
English audio can mean Japanese voices with English subtitles
An English-language audio edition need not be dubbed. Eisys's announcement of translated audio describes keeping the original Japanese performance and adding translated subtitles.
That distinction changes how you will use it. Someone who wants to listen while walking has a different need from someone happy to read subtitles on a screen. Look for whether the translation is subtitles, a text attachment or an English recording, then check the specified player.
Finally, language support does not establish device support. A Windows game remains a Windows purchase unless the listing offers another supported version. If you are buying for your phone, check DLsite games on an iPhone before assuming an English edition will run there.