Including field data within a URL

Including field data within a URL

Hi, 
I'm trying to embed some fetched data into a URL to send out in an email but struggling. 

I have a field against a user called Calendly Username which i'm fetching from that form. That is all working fine. What i'm struggling with is using that data as part of a URL link. Essentially what i'm trying to do is create a URL such as https://calendly.com<<Calendly_Username>>/30min so that I can send out an email to job candidates for them pick a date and time for an interview. 

Any help would be much appreciated.