These instructions are for the original v60 / v66 / v70 and the Motorola E360.  
For the newer v60i/v66i instructions click here.

1.  Locate your ringtone composer

To locate the composer on the Motorola phone click the menu (top central) button and scroll down and select 'Settings'.   A new menu will appear, so scroll down and select 'Ring/Vibrate', then again scroll and select 'My Tones'.

You will now see a list of tones you have entered in the past (the list will be blank if you have not used the composer before).   To store your new ringtone, scroll down to the bottom of the list and you will see '[New Tone]'.  Select this.  On the next screen you will see '[Notes]',  select this.

2.  Enter the key press sequence

Once you have located the composer,  you need to enter the key press sequence given to you by the ringtone converter software.  Look for the text similar to that in the image below, highlighted in yellow.

Now (in the phones composer),  simply type these numbers into your keypad.  The display will show the text below the area highlighted in yellow - nothing like the numbers you are pressing,  but don't worry,  as long as you press the keys in the sequence shown by the software (in this example 1, then 1, then 2,  then 0 etc.)  the tone will go into your phone and play correctly.

3. Save the tone

Finally,  use the save option to store the tone for use.  You will need to enter a name for the tone so you can recognize it later in your phone ring tone list.  Once you have saved it you can play it!

If the tone doesn't sound right,  you have probably missed a key so you may wish to try entering the key sequence again,  press and hold the 'c' key to clear the current notes.

That's it - it could not be simpler,  or cheaper to add a new ring tone to your Motorola phone (as often as you like!)