Welcome to the forums!

I'm going to answer all 3 questions offered by Pixelpest just incase you do mean all 3:
1: To add levels to a world map in an episode: locate the tab called "levels", you will find basically these graphics of a path or similar with a circle inside, tower, pipe, etc. These are levels, and you simply place it onto a world map. To link it to a level, right click on it and select "properties". You will see an option called "level file"; you can either press the browse button to find a level in the episode, or manually type the file name of a level.
2: To upload your levels, episodes, or graphics (it's all the same method), first you will need to zip them up. Right click on the folder that contains the stuff you want to upload, then press "Send to -> Compressed (Zipped) file". Then, go to a site like Mediafire or Dropbox (you may need an account, especially if you want to upload a lot of levels). Then, use the site to upload a level from your computer. Here are a few links to tutorials i found that you may want to look at:
Mediafire:
Dropbox:
3: To share your levels, episodes, graphics etc onto the forums, take the share link from the site you used. Then on the forum, create a topic and put the following onto it:
Download link: <download link>, replace the <download link> with the download link from that site.
You will need to add an image to the topic as per forum rules, to do so you need to use a site like imgur then copy the image file to the forum.
Imgur:
Hope i could help!