Once you have launched the mobile app, just click the "Settings" tab along the bottom of the page and, assuming you are not already logged in, you should see an interface labeled "Auctiva.com Login" which prompts you to enter the username and password associated with your Auctiva.com account.
From there, just enter your credentials in the provided fields and click the green "Login" button and you should be logged into the app. At that point, you should see "Hi, lookandbuyme" across the top of the "Settings" page.
After you are logged in, you should then be able to click the reach the listing creation page by clicking the “Listings” tab along the bottom of the page and then clicking the “Create Listing” option.
You should be able to select the eBay category you would like to list to and enter all other required information when creating listings through the app, but it is not currently possible to select templates nor create multi variation listings through the mobile app.
I hope this helps!