First of all you need to upload the resourcepack to a site in which the file stays on it forever (file.io links can only be used once, so, for example, you could use dropbox or mediafire.)
Once you've uploaded it copy the direct download link (direct download links instantly begin downloading the file once you visit them), if it's a dropbox download link change the last dl=0 with dl=1 then head over to the Settings tab on your panel, and go to the Resource Pack setting. Paste the link there, click on save and restart the server.