You can use PUT which will create or update the value of any cell. You don't need to use delete unless you want the new version to not have some of the old cells .
say we have
r1:f1:c1:value1
r1:f1:c2:value2
you can put r1:f1:c1 new value and you'd get:
r1:f1:c1:new value
r1:f1:c2:value2
Note that actually each cell is stored as rowkey, column family, cell, timestamp, version and value. So depending on how you set versioning (per column family) you can also access the old values including doing a point in time query to see deleted values.