When you join a Bidr event and click on the link you are texted you will first be asked to login.
Your mobile number is always your Bidr "user name" and if you've used the system before it will remember you.
Once you enter your mobile number you will be texted a pin number and then you'll be asked to set a password.
After you set your password you will be on the home page.
From here you can scroll through the shown auction items or click the three horizontal lines on the bottom right of your screen to get to the menu.