Well, once our System has received your payment, activation is done instantly!
You can start uploading your files within seconds; please take in concern that you might need to use the Temporary URL provided in the New account information email sent from us, if you did not yet assign our Nameservers to your Domain (even then, you need to wait for DNS propagation to take place).
Have any other questions? Feel free to ask us! We're live 24/7.