There are several options for installing your license - either through the application interface or via FTP or SSH/SCP.
To install your license via the application, your web server (that usually means Apache) needs to have write permissions to the directory:
In your browser, go to http://your_browsercrm/licence
By FTP or SSH, copy the licence.txt file to the location
Note that the licence.txt file is with the British English spelling of “licence”.
Ensure the file permissions are set to be readable by your web server.