Where should I start with pruning this rose?

Hello there! I’m looking for some advice on pruning roses.

I moved into my new house last summer, and there was a gorgeous climbing rose in full bloom over the door. I kept up with dead-heading but didn’t do any pruning over last winter; this year’s bloom wasn’t as good as last year and the plant is definitely looking quite shaggy now. I’ve never pruned a rose before but I think I need to start now! So – any advice, tips, words of wisdom that you could share with me?

Thank you in advance!