First create an account on ThingSpeak.

Then create a new Channel on your ThingSpeak account. Find How to Create a New Channel

Fill Field 1 as Temperature ,Field 2 as Humidity and Field 3 as pressure.

In your ThingSpeak account select “Channel” and then “My Channel”.

Click on your channel name.

Click on “API Keys” tab and copy the “Write API Key”

Open the Solar_Weather_Station_ThingSpeak code .Then write your SSID and Password.

Replace the “WRITE API ”with the copied “Write API Key”.

Required Library : BME280

Credit : This code is not written by me .I got it from the link given in a YouTube video by plukas