Because you already recorded the script, the simplest thing to do is to replace (e.g. within some text editor) the occurences of
<stringProp name="HTTPSampler.protocol">http</stringProp>
with
<stringProp name="HTTPSampler.protocol">https</stringProp>
in the JMX file.
In future recording, it is best to add to the "Test Script Recorder" element a "HTTP Request Defaults" with "http" value of "Protocol" — this way the protocol field will be empty in recorded samplers. See also: "Handling of HTTP Request Defaults" on http://jmeter.apache.org/usermanual/component_reference.html#HTTP%28S%29_Test_Script_Recorder.