For every segment you attach the value sets. And every value set are having some List of values that will be use to account the transactions.
For example - You are having 3 segments Company, Department and Account.
Now you will create 3 value sets for each segment.
Now to enter any transaction, you will have to select the values in these segments. Suppose you operate in India and UK and you incur some expenses in India. You will give the code for each value.
Company Segment -
India - 10
UK - 20
Department Segment -
Finance - 100
HR - 200
Account Segment -
Rent Expense - 1001
Sales - 2001

Now a transaction takes place in India. You paid rent expense -
So the Values you will select in Company segment is 10
Department - 200
Account - 1001
Together it is called as Combination - 10.200.1001

To edit the values in spreadsheet -
1. Download the Chart of account segment values and hierarchies sheet form fusionappsoer.oracle.com
2. Clear the sheet as it has sample data
3. Fill in the sheet with the values for each value set.
4. Convert it to a zip file and upload to Fusion.