Please review these several steps to insure your anonymity on IRC.
If your last name is visible to others, you can correct that by following these instructions.

Please look at Tools>Options by either choosing the command or clicking on the Options icon:
Tools Options Command or File Options Icon

 

In the resulting dialogue box, if there is a '+' to the left of words 'Connect' and 'IRC' click on the '+' to expand those submenus:
mIRC Options
becomes
mIRC Options
Notice that the field called 'Full name:' is greyed out and cannot be changed if you are connected.  You will need to disconnect briefly to be able to edit that field.  First let's check a few other fields while we are in mIRC Options.

 

Click on 'Identd' to see that page in options:
Identd options
In the 'User ID:' field, put something short, simple and anonymous like just your first name.

 

Click on 'Messages' to see that page in options:
Messages options
In the 'Ctcp finger reply' field, leave it blank (or optionally put something short, simple and anonymous like just your first name).

 

Click on the <OK> button to close the dialogue box.

 

Now we will correct the 'Fullname:' and 'Email Address:' fields in the 'Connect' Option.  To do this, you must disconnect without quitting mIRC.  Either use the File>Disconnect command or click on the Disconnect icon:
Disconnect command or Disconnect icon

Now open Tools>Options by either choosing the command or clicking on the Options icon:
Tools Options Command or File Options Icon

In Options, click on 'Connect' to once more get to this screen:
mIRC Options
For 'Full Name:' put something short, simple and anonymous like just your first name (or even the word 'Anonymous').
For 'Email Address:' put something anonymous like 'askme@myisp' or anything else fictitious.

 

Click on the <OK> button to close the dialogue box.

 

Reconnect by using the File>Connect command or click on the Connect icon:
Connect command or Connect icon

 

The mIRC program will remember these changes in the future, so you are done.  Thank you for taking the time to review this.