For sure! Here is what I did:
- Tap the profile icon in the middle of the bar at the bottom of the screen (it might have the text "lemmy.zip")
- Tap "Get Started"
- Select "Log in"
- Type in "piefed.ca", and confirm that you understand the support is experiemental
- Log in with your username and password
The same app can be used to sign in to a number of websites, so that might be the point of confusion. However, once you have signed in, you should be able to use it normally from here on out :)