Book 1, Chapter 8: Master of the Wood

When you were in Buckland investigating the Nazgûl's incursion, you spoke with Fredegar Bolger, who revealed information about Frodo Baggins and the Enemy's Ring. Crebain attacked and may have overheard the hobbit's words.

Description
Stage 1

'There is one who could find these crebain for us, if we were to ask him for such aid... however, he may not see our worries as his. He is known by many peoples by many names. Of old, he was known as Orald to Men, while to the dwarves he was simply Forn. The Elves called him Iarwain Ben-adar, oldest and fatherless. However, in these days, he is known as Tom Bombadil by those few who are aware of him.

'Look for Old Bombadil's house, which lies at the far eastern end of the Withywindle, the river that flows through the Old Forest. He may help you if you ask him in my name, Aragorn. If you discover anything, I would ask that you address it as best you can.

'I wish I could help you in this task, but the safety of my charges comes before all else.'

Tom Bombadil's house is at the far eastern end of the River Withywindle in the Old Forest.

Strider told you to seek out someone named Tom Bombadil and ask for his aid finding the crebain who flew into the Old Forest.