Lost password not working. Need SMTP but I am locked out.

I just installed a WordPress install successfully, and had the admin password emailed to my inbox. The next day my laptop crashed and I lost only the previous day’s email.

I tried to do a lost password request but get the following error:

ERROR:
the e-mail could not be sent.
possible reason: your host may have disabled the mail() function…

I spoke to my webhost and they told me to use SMTP instead of PHP Mail()

That’s fine, except I can’t just add a plug-in; because I don’t have access to the WP-Admin area right now. (Because I don’t have a password)

Is there somewhere that I can just change a string in an existing flat file.

I searched the help files here on WP Support and I noticed some people mentioning to put something in PHP.INI, but no one ever says what to put there.

Bearing in mind I cannot use a plugin right now, in what file should I specify my SMTP server?

Thanks in advance for your help!

DM