Minä aion hyväksyä ehdotuksen huomenna.

aion is the 1st person singular present tense of aikoa, which means to intend or to plan. It literally says “I intend (to)…,” and since Finnish has no separate future tense, we often use aion plus an infinitive to show future intention.
Conjugation of aikoa in the present tense:
• minä aion – I intend
• sinä aiot – you intend
• hän aikoo – he/she intends
• me aiomme – we intend
• te aiotte – you (pl./formal) intend
• he aikovat – they intend
After aion, the main verb is in its first infinitive form, here hyväksyä.

In Finnish, subject pronouns are optional because verb endings alone indicate person and number. You add minä only for emphasis, contrast or extra clarity. In everyday speech you’d typically drop it:
Aion hyväksyä ehdotuksen huomenna.

Yes. Finnish word order is quite flexible, especially with adverbials. You can say:
Huomenna aion hyväksyä ehdotuksen.
This places emphasis on huomenna. In more neutral style the pattern Adverb – Subject – Verb – Object is common, but you can rearrange elements to shift focus.

You normally use the present tense combined with:
• Time adverbials (e.g. huomenna, ensi viikolla) to mark when something will happen
• Auxiliary verbs like aikoa (to intend) or the construction tulla + −maan/−mään (lit. “come to do”) for planned or imminent actions
There is no separate future verb form—context and these tools convey futurity.