If you have select domain validation using auth file, You will need to follow below steps:

1. Download the file provided from our client area.

2. Create .well-known/pki-validation/ folder inside your web root directory.

3. Access to the folder that you have created inside step 2. and upload the file that you have download in step 1.

4. You need to make sure that you are able to access the file that you have uploaded using below URL:

http://www.yourdomain.com/.well-known/pki-validation/[filename.txt]

you may change the filename.txt to the file name of file that you have download.

5. Once done, Please let us know to complete the validation process.

it will take few minutes to get the process complete.