To upload your content, you will need to open the campaign interface.
If the campaign requires a preview:
You can upload previews by clicking “Upload preview” under “Content” on the menu bar. You have to select the photo or video from your computer and hit enter. After the upload is completed, you and the brand can see your content. You have to wait for the Advertiser to accept or reject it. Only if the Advertiser accepted your preview can you start working on your real content.
After your preview has been accepted, you can upload your post(s). To do so, open the campaign interface (click on the campaign in "My Ads"), and click on the "Post" section.
Select the post from your mobile phone's gallery.
Paste the link of your post.
Click finish to send to the advertiser, and finish your collaboration.
If you have any problems uploading your content, you can click on the "How does it work" line to get some help.
This is what it should look like when you have finished.
Now you only have to wait for the advertiser to approve your content, and your payment will be on the way!