Two main forms of account blocks exist - local blocks (on a single wiki), and global blocks (affecting all wikis).
Most blocks are set by the admins of a community, and only stop you from editing or posting on that one wiki.
The name of the blocking admin will be on the block notice you see when you try to edit there.
You may be able to contact the blocking admin by making a post on your own message wall. This is usually still open to blocked users and changes will usually be seen by others in the community. A link to your message wall can be found under the profile menu at the top right of any page.
Alternatively, you can try contacting the admin on their wall on Community Central and ask for a review of the block.
If these options are not possible in your situation, then you will likely have to wait for the block to expire or join one of the many other Fandom communities available.
However, if you believe your block breaks Fandom policy, please see 'How blocks should be appealed' on that page for how to proceed.
If your block is global (preventing you from editing all wikis), please contact us.
In order to look into your global block, we'll need some additional info. You can find this info when you try to edit a page - you will see a message titled "Your username or IP address has been blocked", similar to this:
(Note: the above screenshot is just an example - these are not the details for your block.)
Please copy and paste the contents of that box, or send us a screenshot.
At minimum, we need to know the block number, which will be labeled "Block ID" in that box (you may need to expand the box or scroll down). Just let us know that information and we will look into why you are blocked.