Not able to connect Postman with my Salesforce Account and send requests


I tried many times to connect Postman with Salesforce but with no success.
Each request I create returns a “401 Unauthorize” response" with the following message": “Session expired or invalid”, “errorCode”: “INVALID_SESSION_ID”.
I was able to generate an Access Token but not with a grant-type “Authorization-Code”, only using “Implicit”.
Even using this Access token, I’ve the same message.
Can someone who is working with Salesforce too can help me please ?
Thank you for your help !