Lets make it really simple.
Since, you have got the transcripts, it must have been provided to you by the University in a sealed envelope.
If you have opened it,then you need to get the transcripts again & provide that sealed envelope as it is to WES.
You do NOT need any other attestation done, & moreover WES does NOT accept any attested copies, just send one set of photopcopy of your mark sheets n degree along with the sealed envelope of transcripts.
Anybody saying anything different from above, is mis-guiding & needs to refer WES website again.