If you are opening an extract obtained from the platform that contains unicode characters, you will want to follow the following process to open these documents. 

Within Excel, navigate to the Data tab and select the option From Text/CSV

This will open the file explorer for you to select the document

From here, you will have the ability to open the file as UTF-8

Often when copying data from an excel worksheet, the data may be encoded as "UTF-8-BOM". Files uploaded need to be uploaded as "UTF-8" to be ingested correctly into the platform. Its a good practice to check the encoding of any .csv or .txt file before uploading. This can be accomplished via txt editors. Simply open the file in notepad, and save as "UTF-8".