To connect your iTunes or Google Play (or both) accounts, go to your Account Settings -> App Store Accounts, and there you will be able to Go to your Connect Account and add your personalised Priori Data email as a new user, and assign the role accordingly.
Connecting your Developer Account is beneficial for both sides: you get a discount + the ability to see estimates for your own apps for free, and we get more data to train our estimation models, which makes our estimates for all apps in your category and market tier more accurate and you more happy. Here's the reason why:
If you aren't aware, the accuracy of our estimates depends on two kinds of data: publicly available (e.g. app store ranks, metadata, ratings and reviews, etc.) and proprietary (e.g. download & revenue data, shared by our Publisher Partners). By getting access to your Connect Account, we see how many downloads and revenue you have to be able to understand the value of your chart position, which helps us predict the amount of downloads and revenue for other ranks. This means that the more Publisher share data with us, the more we know about app store ranks, and the more accurate data we have for you to analyze.