Step 2 : if you succes to download Nessus. Now, you must find Activation Code. You can get that Activation Code in this Link .
Step 3 : After you Registered, you Have got Email.
Step 4 : Install the Nessus who you download.
Step 5 : Run /opt/nessus/sbin/nessus-adduser to get account login.
Step 6 : Input your Login Account.
Step 7 : Input your Activation Code
Step 8 : Now, Nessus will Patching ...
Step 9 : Now You Can Login Nessus
Step 10 : Congrad ... You Succesfull Installed Nessus.