Usually you just import the main sytling class like we normally do, however, the styling references are a bit messed up and need closer investigation and verification on how to fix it.
There is ideas like turning import paths like node_modules/bootstrap-vue/etc into just bootstrap-vue/etc or using the tilde operator ~bootstrap-vue/etc
The reason is because we use a monorepo workspace now, the root node modules is now no longer at the same level as forge ui,