Downloaded tapatalk to find a solution for you.
First,Enter a thread.See that circled (+) sign? tap on it.
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You should be brought to here v
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Tap on the picture that is circled in red,and you should be able to access your photo album,there you tap on the photo you want to upload and it'll automatically upload for you.
If you're talking about creating an album and uploading a photo in it,I'm afraid that's not possible as tapatalk doesn't allow you full access on your profile.
What i'd recommend is to use your phone browser to use era-go instead of tapatalk since it's no different from the PC ver.what you just need to do is tap on "full site".