I'm using the Devanagari-QWERTY keyboard on a Mac so I'm not sure if this would apply to the regular Devanagari keyboard as well, but hopefully I can help.
वृ is just the letters व + ृ written together, so v, shift + r.
द्ध is a conjunct of द + ध, so d, f, shift + d on the Devanagari-QWERTY keyboard.
ॉ is shift + q
Hope that helps.
-Ryan