Formula to auto categorise bank transactions

Hi everyone, I'm trying to put a formula in to auto categorise my bank transactions. I have the transactions in my main sheet as:

Date | Amount | Description | Category

The first three are populated from my bank transaction download, and category is where I want the category to auto populate.

I've tried using VLOOKUP but can't get it to work. I'm fine to create a merchant/data table on this sheet or another:

Merchant | Category

Eg:

Woolworths | Groceries

I want the formula to look at the Description cell for any of words in the Merchant cell. When it finds a word, I want it to put the corresponding word in the Category column from the merchant table to the Category column in the bank transaction section.

Thanks