Ramakrishnan
If the bride and groom have already been entered in the tree. go to either of them and click on the drop down menu by their name and click on "add Spouse".
When the new page opens click on "If this person already exists click here"
Then select the drop down for the surname (family name) then the given name. Once you have found the husband or wife click "Add this name".
You will then have the two as married and each in their own family line. Entering the marriage details on one will then show on both of them, but only after you have linked them together.
Hope this helps.