Visitors coming to the UK for a conference, meeting, or training are eligible to apply for a Standard Visitor Visa. You can learn more about the Standard Visitor Visa, and the visa requirements from your respective country, from the following website:

To apply for a visa, you must first complete an online application and pay online.  You will then be prompted to make an appointment at a visa application center. The following website has more detailed information on how to apply, where to apply, and what documents you will need:

Standard Visitor Visas can only be issued within 3 months of your expected travel date.  However, please allow enough time for visa processing.