For other people to communicate with you using PGP (encrypted message), you must either provide the public key (not the secret key / private key) either directly to the target person or upload it to the Key Server.

There are many Key Servers that you can use to upload a public key, for example:
https://pgp.mit.edu/; http://keyserver.ubuntu.com/ etc.

Open a terminal and type the following command (I made an example using pgp.mit.edu):

Replace [key ID] with the key ID of the PGP Key Pair that you have.
To find out the Key ID, type the following command in the terminal:

The character above your email name is what is called the key ID.

Here's an example of my public key:
https://pgp.mit.edu/pks/lookup?search=0x58BC997445D96F68DB65C169A2CA884F183D22E9&op=index
http://keyserver.ubuntu.com/pks/lookup?search=0x58BC997445D96F68DB65C169A2CA884F183D22E9&fingerprint=on&op=index