Hello Radhika,
Once your contract is signed you should receive an email from SAP Team informing of your tenant URL, initial user and password.
First Email with below information.
Initial user and access information for your SAP ByDesign System
System Information:
Category: Customer Test
ID: )0000000XXXXXXX
URL: https://myXXYYZZ.sapbydesign.com
Logon Information:
Initial User: 000XXXXXX
and
Second email
Initial password for your SAP SAP ByDesign System
Your initial password: XXXXYYYYYZZZZZ
you can log in with this user and create a new business user to proceed further.
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Additional information for SAP bydesign overview - youtube learning
How to contact support - SCN Blog
http://scn.sap.com/docs/DOC-70356
Regards
Leo