Glad to see you here in the Community space, @prashant3.
You can change the ledger to active by going to the Chart of accounts. Let me show you how:
The following article contains additional information about this process: Delete or Make an Account Inactive.
Also, the following resources are good references to learn more in managing and organizing your chart of accounts:
Please know I'm only a post away if you have any other questions about activating an account or other concerns about QuickBooks. Have a nice day ahead!