Add weblinks into APM main login page.

Yes you can, best option would be to look at Advanced Customization:

Access Policy  ››  Customization : Advanced

In here you need to locate the

logon.inc

file,

Customization Settings
> Access Profiles
  > 
    + Common
    + Logout
    > Access Policy
      > Logon Pages
        > Logon Page
          + http_401.inc
          + view.inc
          + logon.inc

This is a HTML page with some javascript and some tokens. Find the

for the start of the main HTML which you can play around with to add some static links into.

NOTE: If you do an upgrade on the F5 device you are likely to lose all your customization changes so back them up so you can reapply them post upgrade.