If you signed up for Slate Plus on the Slate website...
1. Go to the menu in the upper left corner of the app
2. Tap LOG IN / SIGN UP
If you signed up for Slate Plus through Slate's iOS app...
When you purchase Slate Plus through the app, your subscription is tied to your Apple ID. Make sure you are logged in to the App Store on your device with the same Apple ID you used to purchase your Slate Plus subscription.
If that doesn’t resolve the issue, use the Restore link in the Slate Plus roadblock pop-up to retrieve your account from Apple.
If you want to access certain membership benefits outside of the iOS app, you’ll need to associate your iOS subscription with a member account on Slate’s website. To do that, follow the instructions here.
If you were able to sign in but are still having problems accessing your Slate Plus podcast benefits, follow the instructions here.