When you purchase a license you will be sent an email with a license file attached, however depending on your email client/server software sometimes the license file will not be attached as a file, instead the contents will be embedded in the message.
The contents is a single string of text similar to:
9aIzEuMS40IzIjcGF0cmlja2Ryb29uZXlAdGVsdXMubfdfdfd9aIzEuMS40IzIjcGF0cmlja2Ryb29uZXlAdGVsdXMubdfdf9aIzEuMS40IzIjcGF0cmlja2Ryb29uZXlAdGVsdXMub
this needs to be put into a file, this file can then be used when prompted to install the license.
The name of the file does not matter but it is important to save the file as a plain text file, if you save it as .doc file or rtf file for example you editor will convert the contents into its own format, and it will no longer be a valid license key.
Alternatively if you have access to an ftp site or similar we can upload the license file for you there.