That's a good question.
First of all, practically, there's working to make sure that in the October version of the universal periodical review of human rights, the issue of Iran's human rights will be addressed. For that, I believe that your country should work by July.
Also, your country can ask other countries to put requests for Iran to allow international observers inside the country, even though Iran may not accept. That would have a direct impact on having a sort of competitive election. Still it's far beyond a free election.
Second, Iran could be asked to take a small, but effective measure, such as publicizing the result of each polling station. This is very simple. That would prevent systematic fraud. Also, we should empower citizens to monitor and report fraud.
Technically, it's asking Iran to be transparent, and even if Iran doesn't want to change discriminatory laws, holding transparent elections is important.
This pressure should come through Canada, through the European Union, in any negotiations on human rights issues. This issue should be brought up with Iran's diplomats around the world. In general, there should be political pressure. Use all diplomatic means to address the issue of free elections inside the country.