I found the php.ini file on my server in the root directory, and the suggested change worked instantly! ??
However, a caveat: I originally assumed that the ini file would not be there, so I tried the .htaccess approach with very bad results. I tacked the two lines to the end of the file, and my site went down immediately. I started getting 500 errors indicating that the server was not accessible. Fortunately, I was able to FTP the original file back in place, and all was well. Then I looked for the ini file, which I found and fixed.
The moral: Be sure you have a way to undo anything like this that you do before you do it, because the results can be unexpected and very, very serious. ??
Thanks for the tip. It was the third time this week I ran into the file size limit, and I decided to just fix it once and for all, which with you help, I did.