How to include bootstrap plugin without calling widget?

Question

Yii

Good afternoon.
I ran into a little difficulty, I can’t find the answer, how to connect js plugins without calling the bootstrap widget?
for example, the same Alert, or FileInput, how to display all the necessary css, js on the page?
Now I’m calling the widget, just so that it all loads, but somehow it’s all a crutch (
UPD. I also didn’t find any explicit connections in the widget code, so that they can simply be inserted into the page