the articles posted by Ricky are very good, but unfortunately they don't answer your question.
To solve your problem you should try this piece of code:
ExeConfigurationFileMap configMap = new ExeConfigurationFileMap();
configMap.ExeConfigFilename = @"d:estjustAConfigFile.config.whateverYouLikeExtension";
Configuration config = ConfigurationManager.OpenMappedExeConfiguration(configMap, ConfigurationUserLevel.None);
If need to access a value within the config you can use the index operator:
config.AppSettings.Settings["test"].Value;
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