first create a private sign key in b4i by tools / private sign key . This will create some files in your keys folder. Also create an wild card app id like com.example.test* ( later when you are making your first app you need to type com.example.test11 for example in package name textfield in build config)
1) Go to ios dev center
2) Select certificates , identifiers & profiles
3) click certificates
4) click the plus icon on right top
5) select appstore and adhoc under development
6) select continue and seelct the csr you had created at very first step.
this will generate you a certificate file copy it to your keys folder
than create a provisioning file and select your test devices which you added their udids, and tie it to certificate you had just created when it asks. Then copy the provisioning file to keys folder also. You are good to go. Dont forget the install b4x.com/ca.pem to your test device.
MAybe i missed some points , you can better understand with the tutorial video.