Hi Rajinkumar,
Some cloud environments create the administrator account automatically for you. In those cases, you should set the password already design-time. In Studio Pro, go to the App Security (third item in the project explorer) and go to the tab Administrator. There you can set a not-so-stupid password. For security reasons, it's also recommended to rename the administrator, as MxAdmin is easy to guess.
In the case that the administrator account is not created automatically, you can either set it via a microflow (which you for example call from the After Startup) or via overview & edit pages. Make sure you don't enter stupid password there either.
Good luck!