The challenge based system allows direct match requests and seeks. To post a seek to the seek graph, go to Board's Option button - Find a Game on menu. The left tab on top of Find a Game will switch it from seeking to seek graph. Green is regular chess with a human on Seek Graph and solid is rated and hollow is unrated. Guests can only play unrated. Blue is computers. Other colors are variants or loadgame. To rematch the last opponent go to Actions button then on menu, rematch.
On FICS if one has opened one of one's recent games or loaded PGN the user is in Examine Mode on FICS and can't seek while examining. This is not an issue on ICC. Go to Board's Action menu and select unexamine or type unexamine in Main View.
In seeking as guest on FICS, there is a default formula on FICS of Blitz or Standard games. Blitz is 3 minutes to under 15 and standard is 15 and up and this also excludes variants. If not seeking Blitz or Standard, have use formula off in seek form of Find a game Option, or type help formula on FICS to change it. ICC guests have no default formula.
Guests on ICC cannot directly challenge but can be challenged by members. FICS guests can challenge. If it's not a rematch the only way to directly challenge a friend on FICS is to type match username time inc. I.e. match rookers 5 0. Guest match requests will default to unrated.
To Withdraw ones seeks and challenges, the Find a Game option, Pool tab, withdraw challenges, can be used.
The variant option to change from Chess is at bottom of seek form on Find a Game Option, so scroll it down to see this if out of sight. Diamond offers main wilds on FICS. On ICC Diamond offers more, and the more popular ones are further down the list.