Create a relation set
If you want to define relationships between elements and components, you must first create a relation set. Please read Relation sets for descriptions of the two types of relation sets you can create.
1. Click Relations and then, in the Relations Mode group, click 
Assembly or 
Parametrics.
Assembly or Parametrics.2. Click Relations and then, in the R-Sets group, click 
New.
New.3. Select a part or assembly for the Owner.
4. The Attachment field determines whether the relation set is saved in the Contents or Instance file.
5. Type a Name, if desired.
6. Click OK
to complete the operation.
to complete the operation.