There are two ways that an affiliate can have their password reset.
Affiliate resets their own password
If you're an affiliate, you can go to the Tapfiliate sub-domain of the affiliate program you're a part of.
Then, click on the "Sign in" button at the top-right > Forgot password link. A page (or window) will open, where you can indicate the email you used to sign up for the program.
If the email submitted matches one in the program, the reset link will be sent. This link will remain valid for 24 hours.
Advertiser resets the password for the affiliate
If you're an Advertiser, you can launch a message containing a temporary password, which an affiliate can use to gain access to the platform.
This can be done by clicking on the affiliate. In the side-panel, click on the three dots at the top. The option to reset the password is located here.