Click to Call in Salesforce is controlled on the account level, so you'll need to have the administrator of your Yesware account enable/disable it. To do so, your administrator will need to do the following:
1. Select My Account from the Yesware drop down in Gmail.
2. On the next page, select Account > Account Policies.
3. Use the check box to enable/disable Click to Call in Salesforce.
The direct link for this page is: https://app.yesware.com/account/policies.
After doing those steps, everyone on the account will need to refresh Gmail and then refresh Salesforce (in that order) for the change to take effect.