So you don't have a email app on your phone? If you do, then that app should show up in the previously mentioned options, and when chosen, there should be an attachment in the email.
If however the attachment is too large for email (e.g. Gmail wouldn't allow over 20-25MB), then that is where it gets tricky... I used my dropbox account to share a log attachment in the past... but that is a whole 'nother process.
As for the actual log file... it might be in your phones download folder?? it should look like this with current date: blynk_2017_04_17.log