You have a couple choices. You can create a cash account; call it Fixed deposits, and it will be included within Cash & cash equivalents by default. Then, you would have to drill down in Cash Accounts to see the fixed deposit component.
The other alternative, giving you immediate fixed deposit visibility on the balance sheet, is to create a custom control account called Fixed deposits. Assign it to the Assets group. Indicate it is made up of cash accounts. Create individual cash accounts for the various fixed deposits and assign them to the Fixed deposits control account. The procedure is almost identical setting up credit cards as liability accounts:
https://forum.manager.io/t/setting-up-credit-cards/7035/1
The only difference is that you assign the custom control account to Assets instead of Liabilities.