In order to apply i18n to your Confluence macro you need to specify i18n-name-key attribute in macro definition:

<xhtml-macro name="my-xhtml-macro"
             i18n-name-key="com.technerium.my.macro.name"
             class="com.technerium.MyMacro"
             key="my-xhtml-macro">
    <description>My Macro Description</description>
</xhtml-macro>

The attribute value should point to your i18n resource.