To increase the number of materials in Storeroom, first, click on Storeroom in the navigation bar.
Select your Storeroom (Signs and Signals in this example).
In the Materials pane, select the material.
In the Receive Material pane, enter the Account, Transaction date and enter the Quantity to be added to the Storeroom. Then click 'Add to List'.
Review the items to be added under Material to Receive and click Commit.