To connect to your Tradovate account as well as an Evaluation Service account in the NinjaTrader Desktop platform, Multi-Provider Mode must be enabled.
To enable this, select Tools > Options from NinjaTrader Desktop's Control Center:
From the Options dialog box, click the box next to Multi-provider:
Click OK, then restart NinjaTrader Desktop.
Now, when you load the trading platform, you will be able to manage your connections to providers by clicking Connections > configure within NinjaTrader Desktop's Control Center window:
To add a connection to your Tradovate account, double-click the NinjaTrader option, then click My NinjaTrader to add your username and password to your Tradovate account: