adding a blogger blog sitemap to Google webmaster tools - Google Search Console

Google webmaster tools is now Google Search console. So, the way to add a blogger blog's sitemap, from the blogger console, is to go to Google Search Console using the link as in the screenshot below,
Blogger --> Settings --> Google Search console under Crawlers and Indexing

Then the steps given at
https://xomisse.com/blog/create-and-submit-a-sitemap-on-blogger/
for adding sitemap - On the left click Crawl --> Sitemaps --> Add/Test Sitemap.

Enter sitemap.xml in the sitemap field and test for errors, and if OK, redo the steps and submit.