Do you have the pet doggo already? You have to have completed main story quest 1 and also done trald's hangout event in the park. Then followed up with Kuri to get the doggo.
You need the Inflation kink on for any of the doggo's events, so make sure you have that. After that...
For the Park event, you need to get the doggo following you from home during the night and then go to the park with him and play with him during Late Night. Do note that there's only a 1/3rd chance of the park sex scene happening, so maybe drop a save right before trying it to make it easier to get it.
And the event in the house with Trald requires the same, but you have to play with the doggo at Night and, again, only a 1/3rd chance.
I assume you're playing on the Patreon version? This won't be available in the public version until the 8th.
I assume you mean the "Trald At DOR" event? You can find details and requirements for that event over here: https://summoned-by-accident.fandom.com/wiki/CV_Arena
There is also a separate Trald CG scene once you get the doggo. That one's called "Trald Doggo House Funtime A", which you can find over here: https://summoned-by-accident.fandom.com/wiki/Player%27s_House
Patreon version only for both, obviously, though that will change as of the release tomorrow.