Attend caucus
Caucus is a neighborhood meeting of Republicans. It is not a government hearing, and it is not run by this site.
People at caucus elect precinct committee people and pick delegates for later assemblies. You generally have to be affiliated as a Republican to take part. Confirm that rule, and the affiliation deadline, on the Secretary of State and party pages before you count on it.
The Colorado GOP publishes a caucus locator at caucus.cologop.org when a caucus is coming up. That site is not always online between cycles. If it does not load, use the county party and colorado.gop.