Infinite Scrolling - Tumblr Theme Options

[bouda]

I am very novice so if anyone can help, I will need to know exactly where to put the code into the html. I have searched and tried multiple coding, but nothing has worked for me and maybe I was just putting things in the wrong place. I am looking to do two things to a tumblr site I have started to build out. A sample of the site can be found here: https://workingproject1.tumblr.com

1. add infinite scrolling so that photos load when you scroll down. This use to and now it has stopped.

2. remove the "top" button that pops up after you scroll down some on the site, and add a better version of this button - possible an arrow that hovers, and is more user friendly when someone is on the site on their phone.

I truly appreciate any help you can give!