Since you can see the plan you should be able to see 3 & 4 from my first post which can get you started on tuning.

You can force the query to execute with parallelism by applying the Query hint OPTION (MAXDOP 1) at the end of the query like this:

Select * from table Where column = value OPTION (MAXDOP 1);

For the most part the query shape will stay the same so you should be able to tune from the existing plan. You should start by looking at SCAN operations and the FAT lines that signify more rows being processed as those operations are what usually cause parallelism.