If you don't have an account on Tumblr yet, visit their website and sign up before connecting Nembol.
Connect Nembol to your Tumblr account
Tap on Channels in the Nembol app then select Tumblr. Tap Login and enter your email and password. Confirm and you're all set!
Choose your blog
After logging in to Tumblr for the first time, you'll be directed to the Tumblr Settings page where you can choose which of your blogs you want to post your product in. You can access these settings any time by going to Channels→Tumblr→Settings or tapping on Tumblr before publishing a product.