Welcome to the Make community!
I have an example here which you can even import into your scenario How to compress images using TinyPNG via API - #4 by samliew
Please try to search the forum before posting, as others may have already faced the same issue previously. If any previous topic(s) did not help, link to it and state the issues you face trying to implement it.
To set up the API Key connection, you need to also include the text api: BEFORE the API key.
One way to get it encoded is to go to https://www.base64encode.org, type in api: followed by the API key, then click encode.
Paste the encoded part here:
CC: @Audra_Carpenter
Hope this helps! Let me know if there are any further questions or issues.
Note: I see hundreds of posts, notifications, and messages daily on this forum, so if I missed your reply, please message me to look at your reply.
— @samliew
P.S.: Did you know, the concepts of about 70% of questions asked on this forum are already covered in the Make Academy. Investing some effort into it will save you lots of time and frustration using Make later!