Go to your SiteGround account. Click Websites » Site Tools » File Manager » public_html » Click File Upload Icon » then upload the backup you have just saved. Then next, upload Database backup.
After upload, Click-Right on the zip file then Extract. Make sure that the files are on the “public_html” folder. If it is not, select all the files that have been extracted, then Click-Drag all files to public_html folder.
Look for the file named: wp-config.php. Click-Right, then Edit.