Did you read through the codex on how to do things?
http://codex.simple-press.com/codex/plugins/our-plugins/available-plugins/plugin-post-thanks/

I didn’t it but I can not do it now as it says “Existing Members: If you have purchased a support membership and do not believe it has expired, please note this site requires logging into separately from our support site. Please log in using the login form at the top of the right hand sidebar using your support site credentials.” but I paid my membership on 6th of august… as it shows the mail received from simple-press

So – did your attempt to log in to the site fail?

Yes if I tried to log it shows the previous message 

everything looks good with your account on the codex…  but I went ahead and did a manual reset of your account… could you please try again?

Thanks!

Now I can access

Tomorrow I’ll follow the instructions and let you know if there is any problem

OK