Send your form to the below address

The prepositions below and above are often used as adjectives, like in the following examples:

• If you would prefer to make a cash or check donation, please send your gift to the below address. 
• Please send your documents to the below address
• From the below information, calculate the final balance to be carried forward
• Please read the below details to know more. 

It is debatable whether this usage is grammatically correct or not, but it certainly sounds more natural with below placed after the noun. 

For instance, ... please send your gift to the address mentioned (or written / shown / stated / given) below. Or simply ... to the address below.

Alternatively, you can replace it with following, as in the following examples:

• Please send your documents to the following address.
• Please read the following details to know more. 

The same applies to the preposition above. And an alternative could be preceding, as in Please send your documents to the preceding address.