If you donot have NX installed then also you can also create a Assembly structure in Teamcenter
Create a new Item - File > New > Item > Assign ID and Rev > Finish.
and then select the Newly created Item Revision -
and Add the BVR by - File > New > BOM View Revision > Ok
You can also add BVR to existing item revison, Once BVR is added to the Item revisoin then it is open the Item in Structure manager and add number of component you want to add to it as mentioned by Amol_XPLM.
Please find attachment for details.
If you donot have the option as described in Image, contact your IT support.