There are two ways to get there:
1. From your inventory page
Open My Inventory and click the "Trade your CS2 reserved items now" banner. That takes you straight into trading your reserved items.
2. From the trade page
On the trade page, open the game-select dropdown in the top right (where you see CS2 / RUST / TF2 / STEAM) and choose "My Inventory." Your reserved items load, ready to trade.
This works for items you bought from the Store that are still in your Tradeit Inventory (not yet withdrawn to Steam). From there you can trade them for other items, or sell them back for balance — the same as any other trade.