I used arduino platform for uploading data to the thingspeak server which is awesome facility provided open source for practicing IoT. You just need to add the library from the lib'rary manager and its done. Go to examples and open up the one with name "Write Voltage". Edit the code a bit. Enter Wifi credentials and also your channel number and key of thingspeak. You can get the key and number by simply registering yourself on thingspeak.
Hope you find this helpful. Stay tuned for watching how to fetch data from thingspeak server.
Thank You.