Well this is a bit of a vague question but I'll try to answer it the best I can.
If you are interested in becoming a seller on MPGH and as I can tell, you are a new member so you will be required to create a service giveaway before opening your service. This is a pseudo vouch copy that new sellers are required to do in order to sell. For more information on service giveaways please go here: https://www.mpgh.net/forum/showthread.php?t=772057
Now, say your thread is already up and you want to sell some things. You can give vouch copies to users that meet the requirements (1500+ posts) if you desire but it's no longer mandatory due to the service giveaway system we have set up.
I hope this answered your question but if you still have more feel free to post them here. My suggestion is if you wish to sell something then immediately go into the Giveaway section, follow the link I provided above for rules/guidelines and how to properly make a service giveaway thread, make the thread and then after that you'll be free to post your service. Service giveaways do have a mandatory duration of 72 hours before a winner can be chosen and your service giveaway to be considered fulfilled.