To use modelsim as the default simulator in quartus, please follow this blog post.
Step 1: Open settings dialog box by clicking Assignment->Settings menu or by using the keyboard shortcut Ctrl+Shift+E. The settings dialog box should appear.
Step 2: Select EDA Tool Settings->Simulation option in the sidebar.
Step 3: Enable test bench by selecting the option Compile test bench.
Step 4: Click Test Benches… button to create test benches. Test benches dialog should appear.
Step 5: Click New button to create new test bench. New Test Bench Settings dialog should appear.
Step 6: In the New Test Bench Settings dialog, provide the name of your test bench using Test bench name.
Step 7: Add all the necessary test bench and implementation files by clicking File name ellipsis button.
Step 8: Click Ok to create new test bench. Test Benches dialog should now list the test bench you created.
Step 9: Click Ok. Click Apply in Settings dialog box.
Step 10: To launch ModelSim simulator, you have to first Compile your design by clicking the Start compilation icon or by using the Ctrl+L shortcut.
Step 11: After the compilation is successfully completed, launch simulation by clicking RTL Simulation icon.