Yes, you can add hashtags to your tweets in the Twitter Poster.
But be careful with hashtags in your tweets. According to the Twitter Quality Policy, they don’t like it when you manipulate hashtags and add the same hashtags in your tweets over and over again. Therefore earlier we had to restrict the hashtags option in the Twitter Poster. With the hashtags pool and randomization feature, you can again add hashtags to your tweets.
We strongly recommend using a sufficient pool of hashtags to ensure their randomization in order to avoid penalties from Twitter.
Note: don't use hashtags in the Posting mask option, they will be automatically removed.
Go to the Twitter Poster manual to learn more.