How to apply Api key in a flow?

[#1]

Hi I've created a simple Verify Api Key policy, and when I apply to a Pre-flow it works fine. But I would like to apply for a Flow. How can I do it?

<PreFlow name="PreFlow">
        <Request>
            <Step>
                <Name>Verify-Api-Key</Name>
            </Step>
        </Request>
        <Response>
        </Response>
    </PreFlow>

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<VerifyAPIKey async="false" continueOnError="false" enabled="true" name="Verify-Api-Key">
    <DisplayName>Verify-Api-Key</DisplayName>
    <Properties/>
    <APIKey ref="request.header.x-api-key"/>
</VerifyAPIKey>

I'd like to apply here:

<Flow name="put /v1/myresource/{Id}">
            <Description>get resource by id</Description>
            <Request>
                <Step>
                    <Name>Verify-Api-Key</Name>
                </Step>
            </Request>
            <Response/>
<Condition>(proxy.pathsuffix MatchesPath "/v1/myresource/*") and (request.verb = "PUT")</Condition>
</Flow>

Thanks for your help