How to upgrade level of electronic foundry?

click on the building you want to upgrade. It will show you the items it is currently producing and greyed out images of those you have not yet unlocked.

Just above these on the right hand side you can see there are two tabs. Click the tab on the right that has some lines and an up arrow. This will show you how much it is to upgrade, what you get for your upgrade, and a button to click to perform the upgrade.