For creating Dashboard in tableau, First you need to design the worksheets. After designing the worksheet you need to just drag and drop the sheets in the Dashboard interface.Below are the steps to design the dashboard.
Step 1: First import the default sample superstore dataset in to Tableau. Then create a blank worksheet by clicking add worksheet option which is present at the bottom of Tableau interface. and then drag and drop the fields as shown below.
Step 2: Create another blank worksheet and rename the sheet accordingly as shown below.
Step 3: Once you are done with the two worksheets then click on the new dashboard icon which is also present at the bottom. here you can see both the worksheets so just drag and drop those sheets in the blank space. Now your dashboard is created.
You can create more interactive dashboards in Tableau for that you can check tableau tutorial.