IMPORTANT: you have to PRESS TAB EVERY TIME before you borrow things again, or you will LOSE RELATIONS with Friese. Of course, you can repeat the borrowing process as long as you have plenty of space in your inventory.
Go to Dorestad and you can actually sell these 3 items you got for a few hundred penings, at the expense of 10 penings. Exit the town, and his equipments will stay with you. Then press tab to go to the village interface. Find the archery trainer and spend 10 penings for borrowing his bow, arrows, and javelins. You might want to sell some stuff to make sure your inventory can carry a bunch of goods.
After finish the monastery quest you should have gotten some startup money from Jarl Hrodulf Haraldsson to recruit 15 troops. Start doing some quests the people give you. After the plunder of Woden Ric, the player is brought to a doctor near Doccinga.