Hello,
If you don't want the welcome message window to be visible, just leave the edit box empty.
There is no option on removing just the "welcome" word there.
Also, if you want to edit it, just go to Admin Panel > Menu > Main Settings > Welcome Message.
I hope this answers your question.
If you have any other questions, please let me know.
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Thank you again for using iClanWebsites!
Arnulfo,
Customer Care