Hi Chandra kanth,
I'd echo what Joel Acha said about your time dimension.
1. Make sure that at each level of your time dimension hierarchy you have a unique number version of the week in the database i.e. 201605 and use this as your chronological key
2. Look at the content level of your fact table logical source against the time dimension, make sure it's pointing at the right level (most likely Day or Detail)
3. Attempt in the front end a formula like AGO("Fact Sales"."Current Week Sales", "Dim Time"."Time Hierarchy"."Week",1)
These should be the steps you need.
If there's any more detail you could provide that'd be great.