docs: improve translation help

docs/help-translate.md

@@ -8,7 +8,18 @@ Translations are stored in resources (_resx_) files, one file per language. As o
 * English: [_Resources.resx_](/src/BandcampDownloader/Properties/Resources.resx)
 * French: [_Resources.fr.resx_](/src/BandcampDownloader/Properties/Resources.fr.resx)
 
-In order to modify the translations, you can either edit the files with your favorite text editor, or use a tool such as [Zeta Resource Editor](https://www.zeta-resource-editor.com).
+In order to modify the translations, you can either edit the files with your favorite text editor, or use a tool such as [Zeta Resource Editor](https://www.zeta-resource-editor.com). When editing a _resx_ file with a text editor, you will find the translations at the end of the file. A translation looks like this:
+```
+<data name="buttonStart" xml:space="preserve">
+  <value>Start _download</value>
+</data>
+```
+
+Only the `<value>...</value>` tag should be modified. The `name=` attribute should give you some context in addition to the English translation.
+
+Make sure you keep an access key (also called mnemonic) when there is one: the underscore character `_` should precede the letter used as the access key. Ideally, there shouldn't be any duplicate mnemonics on the same window.
+
+## Create a new language
 
 If you wish to create a new language file, simply duplicate the English file (_Resources.resx_) in the same place and rename it using the correct [culture code](https://docs.microsoft.com/en-us/dotnet/api/system.globalization.cultureinfo?view=netframework-4.7.2#culture-names-and-identifiers) (for instance: _Resources.fr.resx_, _Resources.fr-CA.resx_...):